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
Hi, I would like to make this cake but I have only the regular unsweetened cocoa powder. Will that work and if so do I add the same amount?
Thanks.
I love this recipe. I used it as the base for my rustic wedding cake. I replaced the hot water with espresso to make a quick mocha mousse since I love all things coffee. Absolutely delicious! Thank you so much, Sally!
Hello Sally your site is my go-to for all things baked! This cake was a hit on Mother’s Day (which was last weekend where I am.) I used grand cru single-origin dark chocolate, fresh organic butter and cream from a local dairy, and organic flour, and the cake turned out fabulous. Definitely a repeater! Thank you!
Best cake ever! Even my husband was impressed and he’s picky. It tastes like a decadent, high quality chocolate bar. The mousse was light and not overly sweet. This is my new go to cake recipe.
I want to make this cake for my girlfriend’s birthday, but I have to make it a one day a head of the party. How do I store the cake – refrigerate or leave out? Should I make everything first and then assembly the cake the day of the party? Please let me know what the best thing to do!
Debra
Hi Debra, if you can, it would be best to make the different parts of the cake ahead of time and assemble the day of the party. See recipe notes for individual make ahead instructions. Hope the cake is a hit!
I made this for my son’s graduation this week, and it was a big hit! I myself usually don’t like chocolate cake, as most tend to be dry. So not the case here. The crumb is moist and delicious, and the ganache and mousse are the perfect combination with it – not overly sweet, just perfect!
This looks wonderful. I generally try to avoid seed oils and vegetable oils. Could the vegetable oil be substituted for melted butter?
Hi Mollie! We recommend sticking with oil in this cake– it’s the power ingredient providing a lot of moisture to the baked cake. You can try replacing with melted butter, but the cake will taste different and may not be as moist. You can also try melted coconut oil instead of canola (again it will leave a slightly different taste).
Hi. Can I half the recipe for a smaller 2 layer cake
Hi Can i use callebaut 54.5% dark chocolate chips instead of the bars ? and the quantity of chocolate chips will remain the same , that is, 226gm?
Hi Pallavi, we really recommend baking chocolate bars for best results, but those high-quality chocolate chips should work. Same amount. Enjoy!
This is now THE requested cake in our family – we did something crazy though and made some salted caramel sauce and put a layer under the mousse on each layer. Incredible!
Good recipe. The cake tastes like box cake, I added the chocolate chips which all sank to the bottom of the cakes. Maybe dusting them in flour first would help, not sure. The chocolate mousse is good, not way to sweet but make sure you refrigerate for the recommended 2 or more hours first and it’s very cold before assembly. I used the whipped chocolate ganache and it was very good! Thank you for a good recipe.
To make the mousse, can I substitute heavy whipping cream with regular milk?
Hi Stephanie, heavy whipping cream is a must for the chocolate mousse. You need the whipping cream to create stiff peaks!
I really loved the recepie… can i also use this mousse to frost the entire cake instead of the ganache? will it set without melting?
Hi Arpana, we’re so happy you enjoyed this recipe! You could certainly give it a try, but this mousse can melt if left out for a long amount of time. Our whipped chocolate ganache would be a delicious choice, too! Look for the section in the chocolate ganache blog post titled “Whipped Ganache.” Happy baking!
*chefs kiss* turned out fabulous
This was so good and chocolatey. I only had 2 pans and I was a little concerned that the cake would overflow in the oven, but it worked fine and after spending the night in the fridge, it was easy to cut each layer in half. I was hesitant pouring the chocolate in the the whipped cream and concerned that the mousse would not hold up, but it came together beautifully. And the ganache was shiny and the perfect amount. I don’t know if I will ever go back to chocolate buttercream, actually. The entire cake was incredibly impressive, but not very difficult at all.
can there be any alternative for sour cream?
Hi Apoorva, plain full-fat yogurt would be a fine substitute for the sour cream.
I can only find reduced fat buttermilk, is this ok?
Low fat buttermilk will be just fine!
This cake was outstanding and beautiful. I bake quite often and use my family and friends as guinea pigs for any new recipes I try. They are still talking about this cake months later. The Chocolate cake was light but decadent, the mousse filling light, fluffy and delicious and the ganache sealed the deal. I used 3 9″ pans. I had lots of filling left over because I did not have a 4th layer. Used the rest of the filling as a crumb coat and then used the ganache. It made it extra rich having so much filling between layers. Next time I will do 4 layers for a more even cake to filling ratio. Thanks for the great recipe Sally.
Id like to make this cake ahead of time and freeze it after completed. How should I wrap it for the freezer?
Hi Ashley, When freezing a frosted cake you can place the entire cake in the freezer for a short time just until the frosting is set. Once the frosting is solid you can wrap it with plastic wrap or place in an airtight container to store in the freezer.
I followed the recipe exactly as it is written, and my family says it’s the best chocolate cake they’ve ever had! Thanks for always posting foolproof and thorough recipes. They never fail!
In Canada, we only have whipping cream (35%) not heavy whipping cream. Is there anything I can do so the mousse texture is not too soft? What about adding some bloomed gelatin?
Also, does the ganache stay soft even after refrigerated?
Hi Ann, Heavy cream or heavy whipping cream (the two names are often used interchangeably) contain 36% milk fat so yours will be just fine with no other changes (there isn’t much difference between 36-35 percent). The ganache will solidify but it won’t get hard. If you wish to soften it up a bit before serving you can leave the cake at room temperature for a short time before cutting and serving. Enjoy!
Question – when you say to add coffee, do you mean like a cold brew? Instant coffee?
Hi Brittany, you’ll want 1/2 cup (120ml) of hot brewed coffee (instant is fine) for this recipe.
Hi Sally, the cake layers didn’t really rise and I’m not sure why. They turned out more flat and crunchy rather than fluffy. I followed the instructions so maybe I did something wrong?
Hi Daba! It could be a few things. First, make sure your baking powder and soda are fresh. We find they lose strength after just 3-4 months. Use proper room temperature butter and other room temperature ingredients and be careful to just mix the cake batter until combined. Here’s a helpful article about preventing dense cake that may help for next time. Thank you for giving this cake a try!
My first layer cake ever and it was so amazing. The addition of the hot coffee to the cake batter is a must.
How much cups of chocolate chips will I use in the ganache and mousse if using?
Hi Amy, you’ll need about a cup for each.
My mousse is very watery. How can I salvage it!
Hi Prarthna, Chilling it should help re-solidify it. Were you sure to use heavy cream/heavy whipping cream? (Simply “whipping cream” contains less fat and we don’t recommend it.)
I think I used whipping cream 🙁 how doomed am i
Hi Sally, Can you make the cake in advance and freeze it ?
Hi Nila, absolutely. We recommend freezing the cake layers (rather than an assembled cake). See recipe notes for more details!
Can I use cake flour?
Hi Amy, we don’t recommend using cake flour in this recipe. Chocolate cakes already have cocoa powder— which is a VERY fine dry ingredient. The combination of cake flour and cocoa powder usually results in a flimsy cake.
I am not someone who bakes a lot. I wanted to surprise my husband with some cake which is moist, creamy and yum! Most of the cakes we get in the shop/store are pretty dry with a couple of exceptions.
I tried this cake and boy, it was so so good! I guess I will be coming back to your page to find anything baking related.
Thanks so much for sharing this recipe. 🙂
Much love <3
Can I use a regular mousse recipe with this that includes the egg whites and egg yolks or is there no difference in taste between using the simplified version here?
Hi Kimberly, If you have a traditional mousse recipe you love, it should be just fine between the cake layers. Just make sure it’s properly chilled.
I made this for my son’s 13th birthday. The only alteration I made was to make about 25% more mousse so we could put a thicker layer as a crumb coating. The cake was fabulous. Not too sweet, not too decadent, but DEFINITELY delicious. Four 9″ layers, cut into 16 pieces and it was perfect.