This super moist dark chocolate mousse cake combines unsweetened natural cocoa powder and dark cocoa powder for an extra rich flavor. Fill the cake with a simplified chocolate mousse and cover the whole dessert with semi-sweet chocolate ganache. If needed, you can prepare the ganache and mousse ahead of time.
Chocolate mousse is simple divinity in its own right, but when paired with chocolate cake, it’s downright decadent. And then add chocolate ganache to the mix? Have mercy.
This spectacularly rich chocolate cake is such a personal and reader favorite that I knew I had to include it in my cookbook, Sally’s Baking 101 (which has become a New York Times Best Seller!). The cakes chapter just would not have been complete without it!
It’s actually the first recipe in that chapter, and in the book it’s titled “Chocolate Ganache Cake: 2 Ways,” because I include a second filling option—peanut butter frosting instead of chocolate mousse, just like this recipe for dark chocolate peanut butter cake. Both versions of ganache-topped chocolate layer cakes have received such glowing reviews on my website, I simply couldn’t choose between them… so I found a way to include them both!
This cake basically demands a huge gathering because—trust me—you don’t want to be left alone with its temptation. It WILL call out your name each time you open the refrigerator.
Taunting you.
One reader, Judy, commented: “Don’t make this cake unless you want everyone who has a bite to request that you make it for every special occasion for the rest of time 🙂 I do four layers and follow the recipe exactly, and it has come out perfectly every time. I’ve already made at least ten of these cakes. Fabulous! ★★★★★“
One reader, Cecilia, commented: “OMG! This cake is absolutely divine! It’s a chocolate lover’s dream. The chocolate mousse is heavenly. I made it for my niece’s birthday and ended up making a four-layer cake. There were no leftovers. I don’t need any other chocolate cake recipe. This is it! Definitely the best! ★★★★★“
One reader, Brittney, commented: “This cake turned out amazing! I made it for a birthday party… and it was requested to be the new ‘party cake’! ★★★★★“
3 Parts to Dark Chocolate Mousse Cake
Let’s break down each component of this intensely rich cake:
- Dark Chocolate Cake: This is actually a variation of my tuxedo cake, which originated from my chocolate cake recipe. In recent years, I’ve found that replacing sour cream for some of the buttermilk gives the cake more structure.
- Chocolate Mousse: I researched simplified ways to make a fluffy chocolate mousse filling without the use of eggs or gelatin. This chocolate mousse filling combines real chocolate and homemade whipped cream. Or our whipped frosting would make a wonderful alternative filling if you don’t want to make the chocolate mousse!
- Chocolate Ganache: Top the whole cake with 2 ingredient semi-sweet chocolate ganache. You should be a chocolate ganache pro by now!
Video Tutorial: Chocolate Mousse Cake
Stick-to-the-back-of-your-fork moist. This is every chocolate lover’s dream!
Dark Chocolate Cake
Use this chocolate cake as the starting point. For a sturdier, yet moister crumb, swap some sour cream in for the buttermilk and reduce the hot liquid. The acidity in both sour cream and buttermilk is a must to properly leaven this cake. (If desired, see my posts on Baking Powder vs Baking Soda and Baking with Buttermilk for more information.) This cake has a natural dark chocolate taste, but to deepen that flavor, use a mix of natural cocoa and Hershey’s Special Dark cocoa powder. A touch of espresso powder and hot coffee further enhances the chocolate flavor. The cake will not taste like coffee. Rather, the two add depth to the cake’s chocolate flavor.
- Why hot liquid? The hot liquid encourages the cocoa powder to bloom and dissolve. If you don’t drink coffee, you can use hot water.
You have options! You can make this cake into 2, 3, or 4 layers. I highly recommend 3 or 4 layers because there’s over 4 cups of chocolate mousse to spread inside. You can use 8 inch or 9 inch pans. The bake times are similar, see recipe notes.
A cup of chocolate chips adds even more chocolate flavor. I used 1 cup (180g) of mini semi-sweet chocolate chips in this pictured cake, but left them out in the video. They’re optional, but definitely worth the addition!!
You can also see this exact cake batter baked as three layers in both my chocolate peanut butter cake and chocolate raspberry cake (try one of those next!).
Simplified Chocolate Mousse
The chocolate mousse adds a creamy and light contrast to the dark chocolate layers. You need 6 ingredients:
- Hot Water
- Cocoa Powder – natural or dutch-process
- Melted Chocolate – use two 4-ounce chocolate baking bars found in the baking aisle
- Heavy Cream
- Confectioners’ Sugar
- Vanilla Extract
Whisk the hot water and cocoa powder together. Pour into melted chocolate. The hot water breaks up the chocolate, adding to the airy mousse consistency. Cocoa powder creates additional chocolate flavor. Fold this chocolate mixture into whipped cream—a combination of heavy cream, confectioners’ sugar, and vanilla extract.
Whipped cream + our chocolate mixture. ↑
Fold them together to make our chocolate mousse filling. ↓
Baker’s Tip: The chocolate mousse must chill in the refrigerator before using, so it’s a good idea to make it ahead of time or as the chocolate cake layers are cooling. The mousse is best cold, so I actually recommend serving the cake cold. (Additionally, the cake is much easier to assemble if the mousse is cold!)
By the way, this chocolate mousse also makes for a wonderful alternate filling in homemade eclairs!
Chocolate Ganache
I won’t go into a lot of detail about the chocolate ganache because I have a complete chocolate ganache tutorial for you! Like the chocolate mousse, it’s imperative to use pure chocolate. Wait about 20 minutes for the ganache to thicken before pouring onto the cake.
How to Assemble & Decorate Chocolate Mousse Cake
Chocolate ganache enrobes 4 cake layers and 3 mousse layers. Place bottom cake layer on your cake stand or serving plate. Using a large icing spatula, evenly cover the top with about 1.5 cups of chilled chocolate mousse. Top with 2nd cake layer and another 1.5 cups of mousse. Top with the third cake layer, then spread another 1.5 cups mousse evenly on top. (Save a large spoonful of mousse for a thin crumb coat.) Top with final 4th cake layer. Spread any remaining mousse around the sides as a crumb coat. Run a bench scraper around the cake to smooth it out. Refrigerate cake for at least 1 hour and up to 4 hours. Chocolate mousse is pretty fluffy, so the cake won’t hold its shape unless it’s properly chilled.
Pour ganache on top then run a bench scraper around the sides to smooth it out. You can serve the cake immediately or wait for the chocolate ganache to set. 🙂
What About Cupcakes?
Instead of a big cake, you can make chocolate mousse cupcakes. Use my chocolate cupcakes recipe and halve the chocolate mousse and chocolate ganache recipes below. Fill the cupcakes with chocolate mousse using my Sugar Plum Fairy Cupcakes as an example. Drizzle cooled cupcakes with ganache. Eat your heart out!
You can also use the chocolate mousse instead of pastry cream in homemade mille-feuille!
More Indulgent Chocolate Desserts
- Dark Chocolate Bread Pudding
- German Chocolate Cake
- Flourless Chocolate Cake
- Black Forest Cake
- Chocolate Lava Cakes
- Chocolate Mousse Pie
- Mint Chocolate Cake
Dark Chocolate Mousse Cake
- Prep Time: 2 hours, 30 minutes (includes chilling)
- Cook Time: 25 minutes
- Total Time: 5 hours, 55 minutes (includes cooling)
- Yield: serves 12
- Category: Cake
- Method: Baking
- Cuisine: American
Description
This super moist dark chocolate cake combines unsweetened natural cocoa powder and dark cocoa powder for an extra rich flavor. Fill the cake with a simplified chocolate mousse and cover it with semi-sweet chocolate ganache. If needed, you can prepare the ganache and mousse ahead of time (see Notes). This recipe is also in my New York Times best-selling cookbook, Sally’s Baking 101.
Ingredients
- 1 and 3/4 cups (219g) all-purpose flour (spooned & leveled)
- 1 and 3/4 cups (350g) granulated sugar
- 3/4 cup (64g) unsweetened natural cocoa powder* (see Notes)
- 2 teaspoons espresso powder (optional)*
- 2 teaspoons baking soda
- 1 teaspoon baking powder
- 1 teaspoon salt
- 3/4 cup (180g) full-fat sour cream, at room temperature
- 1/2 cup (113g/120ml) vegetable oil
- 2 large eggs, at room temperature
- 1/2 cup (120g/ml) buttermilk, at room temperature*
- 2 teaspoons pure vanilla extract
- 1/2 cup (120g/ml) hot water or black coffee*
- 1 cup (170g) semi-sweet mini chocolate chips tossed in 1 Tbsp flour (optional)
Chocolate Mousse
- 1/2 cup (120g/ml) hot water
- 1/4 cup (21g) unsweetened natural or Dutch-process cocoa powder
- 8 ounces (226g) quality semi-sweet chocolate, finely chopped*
- 2 cups (480g/ml) heavy cream, cold
- 2 Tablespoons confectioners’ sugar
- 1/2 teaspoon pure vanilla extract
Chocolate Ganache
- 8 ounces (226g) quality semi-sweet chocolate, finely chopped
- 1 cup (240g/ml) heavy cream
- optional, for garnish: fresh berries and/or chocolate shavings
Instructions
- Preheat the oven to 350°F (177°C). Grease four 8-inch or 9-inch cake pans, line with parchment paper rounds, then grease the parchment paper. Parchment paper helps the cakes seamlessly release from the pans. (If it’s helpful, see this parchment paper rounds for cakes video & post.)
- Make the cake: In a large bowl, whisk the flour, sugar, cocoa powder, espresso powder, baking soda, baking powder, and salt together. Set aside.
- In another large bowl using a handheld or stand mixer fitted with a whisk attachment (or you can use a whisk) mix the sour cream, oil, and eggs together on medium-high speed until combined. Add the buttermilk and vanilla and mix until combined. Pour the dry ingredients into the wet ingredients, add the hot water/coffee, and whisk or beat on low speed until combined. Fold in the floured mini chocolate chips, if using. Divide the batter evenly among the prepared pans.
- Bake for 19–23 minutes. Baking times vary, so keep an eye on yours. The cakes are done when a toothpick inserted in the center comes out clean. Cool the cakes in the pans set on a cooling rack for 1 hour. Run a knife around the edges to help loosen the sides, remove the cakes from the pans, peel off the parchment, and place on the rack to finish cooling. The cakes may slightly sink in the middle as they cool—that’s expected.
- Make the chocolate mousse: In a small bowl, whisk the hot water and cocoa powder together until smooth. Melt the chopped chocolate in a double boiler or use the microwave. If using the microwave: place the chopped chocolate in a medium heat-proof bowl. Microwave for 20-second increments, stirring after each increment until completely melted and smooth. Pour hot water/cocoa mixture into the melted chocolate and stir until thick and smooth. Set aside. In a large bowl using a handheld or stand mixer fitted with a whisk attachment, whip the heavy cream, confectioners’ sugar, and vanilla extract together on medium-high speed until medium peaks form, about 3 minutes. Medium peaks are between soft/loose peaks and stiff peaks. Pour in the chocolate mixture and gently fold together with a spatula. Do not overmix, as this could deflate it. Cover the mousse and refrigerate for at least 2 hours or up to 2 days. Makes about 4.5 cups (about 900g).
- Assemble the cake before preparing chocolate ganache: First, level the cakes (if needed): using a large serrated knife, slice a thin layer off the tops of the cakes to create a flat surface. Place 1 cake layer on your cake stand, cake turntable, or serving plate. Using a large icing spatula, evenly cover the top with about 1.5 cups (200g) of chocolate mousse. Top with the second layer, upside down, and evenly cover the top with the same amount of chocolate mousse. Top with the third cake layer, right side up, and again cover with the same amount of mousse. Top with final cake layer. Spread the remaining mousse on top and around the sides of the cake as a crumb coat. Run a bench scraper around the cake to smooth out the sides. Refrigerate for at least 1 hour and up to 4 hours. Prepare the ganache while the cake is chilling.
- Make the chocolate ganache: Place the chocolate in a medium heat-proof bowl. In a small saucepan, heat the cream over medium heat just until it begins to gently simmer. (Do not let it come to a rapid boil—that’s too hot!) Pour the warm cream over the chocolate and let it sit for 2–3 minutes to gently soften the chocolate. With a metal spoon or small spatula, slowly stir until the chocolate has melted and the mixture is smooth. The finer you chopped the chocolate, the quicker it will melt with the cream. If it’s not melting, do not microwave it. If needed, see Troubleshooting Chocolate Ganache. Refrigerate the ganache for at least 30 minutes or up to 1 hour to thicken.
- Pour/spoon the thickened ganache on the chilled cake. Smooth the top and sides with an icing spatula. Top with optional garnish such as fresh berries and/or chocolate shavings. Serve cake immediately or chill, uncovered, for up to 4–6 hours before serving. Cake can be served at room temperature or chilled.
- Cover leftover cake tightly and store in the refrigerator for up to 5 days.
Notes
- Make Ahead & Freezing Instructions: Prepare cake through step 4. Wrap the individual baked and cooled cake layers tightly and refrigerate for up to 2 days or freeze up to 3 months. Bring to room temperature, make mousse filling, then continue with step 6. You can prepare the chocolate mousse in advance. See step 5. You can also prepare the chocolate ganache ahead of time too. Refrigerate prepared ganache for up to 3 days. Bring to room temperature before spreading onto cake. You can freeze cake for up to 3 months. Thaw overnight in the refrigerator, then bring to room temperature or serve cold. See How to Freeze Cakes for more information.
- Special Tools (affiliate links): 8-inch Round Cake Pans or 9-inch Round Cake Pans | Glass Mixing Bowl | Whisk | Electric Mixer (Handheld or Stand) | Cooling Rack | Double Boiler | Cake Stand or Cake Turntable | Large Icing Spatula | Bench Scraper | Cake Carrier (for storage)
- 3-Layer Cake: You can also prepare this as a 3-layer cake. Divide batter between three 8-inch or 9-inch cake pans in step 1 and bake for 24–26 minutes or until a toothpick inserted in the center comes out clean. Use about 2 cups of chocolate mousse between each layer.
- Espresso Powder/Coffee: Espresso powder and coffee will not make the cake taste like coffee. Rather, they deepen the chocolate flavor. I highly recommend them both. You can find espresso powder in the baking aisle at many grocery stores or online. If coffee isn’t your thing, you can leave out the espresso powder and use hot water instead of the hot coffee.
- Cocoa Powder: For the best dark chocolate flavor in the cake, I recommend using a blend of unsweetened natural cocoa powder (1/4 cup; 21g) and Hershey’s “Special Dark” cocoa powder (1/2 cup; 43g). Hershey’s Special Dark is actually a mix of natural cocoa powder (an acid) and Dutch-process cocoa powder (a base) and it worked fine in this recipe. This recipe needs acidic natural cocoa powder, so do not use ALL Dutch-process cocoa powder. For best results, use 3/4 cup (64g) natural or the blend of natural/Special Dark I used. For the chocolate mousse, you can use either unsweetened natural or Dutch-process cocoa powder (or the Hershey’s Special Dark).
- Why Room Temperature? All refrigerated items should be at room temperature so the batter mixes together easily and evenly. Read more about why room-temperature ingredients are important. Instead of sour cream, you can use plain yogurt. The cake won’t taste as rich, but it’s a fine substitute.
- Buttermilk: Buttermilk is required for this recipe. You can make your own DIY buttermilk substitute if needed. Add 1 teaspoon of white vinegar or lemon juice to a liquid measuring cup. Then add enough whole milk to the same measuring cup until it reaches 1/2 cup. (In a pinch, lower-fat or nondairy milks work for this soured milk, but the cake won’t taste as moist or rich.) Stir it around and let sit for 5 minutes. The homemade “buttermilk” will be somewhat curdled and ready to use in the recipe.
- Chocolate in Mousse & Ganache: Mousse & ganache will only set if the correct chocolate is used. You can use high-quality chocolate chips if needed (I prefer Ghirardelli semi-sweet chocolate chips), but I recommend using pure chocolate baking bars. You can find them right next to the chocolate chips in the baking aisle. They are sold in 4-ounce (113g) bars. I like Baker’s or Ghirardelli brands.
Reader Comments and Reviews
I’ve made this twice now and it is well received! The dark chocolate lovers LOVED it and the non-dark chocolate lovers enjoyed it too. The first time I made it I spilt the four layers into 2 two layer cakes. The second time I made it as a four layer cake. But my cake tilted. I waited until it was cool to frost and assemble. The layers were even. Any ideas what happened?
Hi Ashlee, was the mousse/frosting a bit on the warm side? That, or even the temperature in your kitchen, could make it a bit more “slippery” and cause it to slide a bit. Cake dowels are especially helpful for keeping cakes upright!
Made this for my dad’s party and everyone loved it! Apparently people keep asking “who made the cake?” Which given I’ve made it for every party for the last 4 years I don’t know whether to take it as a compliment or an insult .
Your recipes always look SO delicious! But you have so many 3-layer cakes, is there any way you can advise on converting to a one layer or smaller for 1-2 people? thank you!
Hi Melissa, this cake pan sizes and conversions guide will be helpful! You might also like these recipes for 1 layer sprinkle cake, 1 layer chocolate cake, and small chocolate cake.
I’m super excited to try this recipe!! I was wondering if the mousse is able to be pipetted to decorate the top of the cake?
Hi Alex, the mousse isn’t quite sturdy enough for intricate piping, but simple piping should hold well. For a more stable option, we’d recommend piping some whipped ganache instead. Hope you love the cake!
Hi, how far in advance can you make the mousse?
Hi Julie, cover mousse and chill in the refrigerator for at least 2 hours and up to 2 days.
Made this for hubby’s birthday cake – he loved it!
I don’t have Hershey’s Special Dark cocoa powder where I live. You recommended using a blend of natural and dutch processed cocoa? What would the weight for the two different cocoa powders? Thanks!
Hi Denise, We recommend using a blend of unsweetened natural cocoa powder (1/4 cup; 22g) and Hershey’s “Special Dark” cocoa powder (1/2 cup; 43g).
Hi I live in a very hot country now. Afraid the mousse won’t stabilize or the cake will melt when I transport it. Wasn’t an issue when I lived in nyc. Is there a recipe where I can stabilize with mascarpone
Hi Sanjana, we haven’t tested a version of this mousse with mascarpone, and it would take a bit of trial and error to perfect. If you can find a recipe using mascarpone instead, feel free to use that between the layers instead. Let us know if you find one you love!
I want to decorate my cake and I was wondering if I could frost the cake with vanilla buttercream???
Hi Lizzie, Sure can!
Hello,
I currently live in Brazil and it is impossible to find sour cream, can I replace it for something else?
Hi Ana, full fat plain yogurt is a great substitute for sour cream in this cake.
I really wish you did weights, it’s so much easier!
Hi Rachel, we include the ingredient weights next to the ingredients on the recipe card.
Hello! I was wondering if instead of coco powder in the mousse recipe I could use espresso powder to make an espresso mousse ???
Hi Autumn! An espresso mousse would require some testing, but we wouldn’t replace all of the cocoa powder. You could try replacing 1-2 tsp of the cocoa powder with espresso powder.
Have you tried replacing the oil with butter? What would that do to the texture and taste?
Hi Sarah, using butter here would yield a day cake. Best to stick with oil for chocolate cakes!
This cake turned out AMAZING!!!!! I made it for a birthday party… and it was requested to be the new “party cake”!
PS- I was able to sub GF flour in for the regular flour with success!
Hi Sally. Love your recipes. Can this be baked as two cakes and torted?
Hi Sora, I don’t see why not, but you’d either need to use larger cake pans or the cakes will be very thick and take a long time to bake through.
Fourth time making this cake. I still get rave reviews. I baked it for Father’s Day/my birthday. I love baking!
My brother requested an extra dark chocolate cake for his birthday and I was wondering how dark this cake is? Should I replace the semi sweet chocolate for bittersweet in the mouse and ganache? Or is it already pretty dark as is? Thanks in advance!
Hi Rey, we recommend semi-sweet chocolate bars. Bittersweet would be quite dark, but you can use them if you prefer.
For those curious, I ended up switching all semi sweet chocolate bars for bittersweet. It was great and definitely not too dark; I could’ve used an even higher cocoa% for a dark chocolate lover! Really fantastic recipe that everyone enjoyed!
Hi Sally… I’ve made this cake many times. And it has been a Hit always. All my friends love it. They say they have never eaten chocolate cake like this. So thanks for your recipe. I’m from Goa – India. And the weather here is mostly very hot and humid, just like Florida. Though the cake tastes heavenly, it becomes really sticky. If I hold it, the whole top layer sticks to my hand. I always make sure that all the ingredients are at room temperature before I mix and bake. I follow the recipe very closely. However, the cake bakes perfectly well but it is sticky on the outside. How to overcome this problem?
Hi Pallavi, we’re so glad you love this cake! You can try adding a little more flour to see if that helps next time.
Would you recommend using Ghirardelli’s semi-sweet chocolate bars or the bittersweet chocolate bars?
Hi Evelina, we recommend semi-sweet chocolate bars. Bittersweet would be quite dark, but you can use them if you prefer.
This recipe is amazing!
This is my all time favorite cake recipe! My whole family loves it! However I have recently been diagnosed with celiac disease and wondering if you can offer advice on modifying this recipe to make it gluten free. Thank u!
Hi Colleen, we wish we would help, but don’t have much experience with gluten free baking. There are plenty of gluten free baking websites with great recipes, though! And let us know if you try adapting this recipe.
Which is better to use 8” or 9” cake pan? What did you use for the picture
Pat, we typically use 9 inch pans for this recipe. 8 inch pans would produce slightly thicker layers.
Sally, what brand of espresso powder do you use? I am having a hard time finding any by me, and was going to order some on amazon.
Hi Nicole, we like to use King Arthur brand.
This recipe was fantastic. The cake itself will now be my new go to chocolate cake recipe.
When I mixed the chocolate mixture together, it became hardened and dry. It was not pourable into my whipped heavy cream. Now my mousse layer looks like chocolate chip ice cream and is deflated. Any tips? Is it supposed to be warm/room temp/cool when it gets mixed?
Hi Sarah, I’m so sorry to hear this! I would be happy to try to help figure out what went wrong. I actually made this cake with Sally just this week, so it’s fresh in my mind. What kind of chocolate did you use for melting?
I used box cake instead of the recipie (sorry not sorry, it’s too easy) but made the mouse and ganache and it turned out AMAZING! Would definitely recommend
I made this cake. The mousse was tasty but the cake fell apart. The mousse was so soft and light that the cake pushed down on the mousse and pushed it out of the cake. I made 2 6″ round cakes..so Idk why it didnt work. I tried cooling the cake in the fridge. Still didnt work:(
Hi Sarah, we’re happy to help troubleshoot. The most common cause of a thin mousse is over mixing. If you try it again, avoid over-mixing which can deflate/thin out the mousse. And also, make sure you chill it in the refrigerator for at least 2 hours before using. For your 2, 6 inch round cakes, did you use a scaled back version of the batter? If you used the batter as written, that will be too much for 6-inch pans and cake the cakes to bake unevenly, which is likely why they fell apart. Thank you for giving this one a try!
I love this cake. Do you think I can double the recipe for a bigger version?
Hi Becks! We recommend making two batches of batter instead of doubling. So glad you love it!
Is there a way to make this without eggs? I love this cake, but I have to make it for people who eat dairy but no eggs
Hi Kosha, we haven’t tested this cake with any egg substitutes, but let us know if you do any experimenting.
Is there a way to make a smaller version of this cake? Maybe a 6” cake? I want to make this for my birthday but we only have 4 people and I definitely don’t need that huge of a cake! Also for some reason I can’t see any of the comments for this recipe.
Hi Neeta, For a 6-inch cake, we’d recommend using this chocolate cupcakes recipe as the batter to make a 3 layer 6 inch cake. See our 6 inch cake recipes post as a guide. Halve the chocolate mousse and ganache from this recipe so there’s just enough. Hope this helps!
Hi I was wondering can I use 74% chocolate in the
mousse and ganache as I want to make it dairy free. I have already managed to adapt the rest of the cake which works well.
Hi Lou, you can use 74% cocoa chocolate for a darker chocolate flavor.