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 made this for my husband’s birthday. Everyone agreed it was decadently delicious. A lot of work, but worth it in the end. The cake was quite dense and hard to remove from the pans, but it really didn’t matter. I will make it again, the nice part was spreading it out over a few days, LOL
WOW! What a recipe! It was amazing, and, as others said, not too sweet even with so much chocolate. I did not frost sides – just put ganache on top with circle of raspberries around edge and chocolate curls in the center. Easy to follow … this was my first ever “fancy” cake and turned out great! Loved that I could make in stages … cake and mousse a day ahead and then assemble the next day.
Sally, you are my “go to” site for everything baking-wise. Your recipes are always amazing with great directions! Thank you.
I’m thinking of making this for my nephews wedding. How long will this cake last at room temperature? Will it get soft/melt?
Hi Sheri, the cake will be fine at room temperature for a few hours. If you can refrigerate it beforehand, that would be great.
It’s a great recipe. Just wondering if I could used black cocoa instead?
Hi Pauline, Black cocoa powder is a dutch process cocoa powder. This cake recipe needs acidic natural cocoa powder, so do not use ALL dutch-process cocoa powder. You can use a mix of both – see recipe notes for details.
Definitely a dark chocolate cake. The mousse was easy to make even with it being my first time. The cake was a tad dryer than preferred, but I ran out of sour cream. So probably baker error on that. Even with it being advertised as “dark chocolate”, which I thought would deter some people, everyone at work loved it.
This recipe is amazing. I needed a good chocolate cake for my chef partner’s birthday, and this one checked the boxes. I’m not much of a baker, but this came together easily, each component was delish, and the final product knocked it out of the park. I cut the recipe in half, and spread a thin layer of blackberry jam under the mousse, and would do both again! So good..
omg… making the mousse was so much fun and so easy. thank you so much!!!!
Hi SBA team! I’ve noticed on all of your layer cake recipes that you divide the batter between more pans rather than say baking this cake in two 9-inch pans and splitting the cake to make four layers. Is there a reason for this?
Hi Sarah Beth, you can do it that way, but the bake time will be longer because the layers will be twice as thick. It’s a fairly crumbly cake, so if you slice the layers in half that way, expect to have a more crumbly surface to spread the filling/frosting on.
I’m thinking of making this recipe, but I only have 2 9-inch rounds. Could I let the batter sit (either counter or fridge) while the first batch cooks and then cook the second batch?
Hi Sarah, You can bake two layers and keep the unused batter covered at room temperature until your cake pans are ready to be used again.
Can the chocolate layers be made ahead, frozen and then thawed before assembly?
Hi Dana, yes, and I do this all the time! Cool the layers completely, then wrap each in plastic wrap. I then stack them together and wrap the stack in a layer of foil and freeze. Thaw in the refrigerator or at room temp–I take the layers out of the foil and place them side by side, still wrapped in plastic wrap for this.
I would love a vanilla version of this cake! Any tips?
Hi Miranda, that would take some testing – it may be best to search for a vanilla mousse cake recipe instead!
I’ve made this cake previously and it’s phenomenal although never did the 4 layers. I only have 3 of each 8″ and 9″. Could you tell me the weight of the batter so I can measure out accordingly baking the last layer solo.
Can you make this into a 2 layer half sheet cake?
Hi Erin, we haven’t tested this recipe for a 2 later half sheet cake, but you can make this recipe as a 9×13 sheet cake (same oven temperature, about 35-40 minutes bake time). If you need two 9x13s, we’d recommend making it twice. Here is everything you need to know about converting recipes to different Cake Pan Sizes.
This is the best cake ever! I feel like I am bringing my “A” game to the kitchen. Thank you for making it easy to try things I’ve never attempted before.
Hey! What do I do differently if I want to make this into a 6 inch cake?
Hey Ana, For a 6-inch cake, we’d recommend using this dark 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 Ana, did you end up using this recipe for 6”
Cakes? What did you do differently if so?
Huge hit with family! Moist, delicious and not as sweet as you would think it would be! The perfect recipe, thank you for sharing!
Love this recipe! It’s my go-to now. Just a question though. Can you cover this with fondant? Thanks
Hi Katrina, this cake should hold up fine under fondant, but fondant covered cakes should not be stored in the fridge.
Only one word for this cake: phenomenal. I’ve been wanting to bake it for years for my birthday but always ended up choosing another one of (your) chocolate cake recipes because this one seemed intimidating. This year, I made it for my sister’s birthday and I’m so glad I did. It’s much easier than I thought, fun to make, and definitely worth it! Every element is delicious, and the chocolate flavor is divine. I used the part Hershey’s Special Dark/ part regular cocoa powder. My dad had a slice and his comment was, “This is a contest winner.” Can’t beat that! My kids loved it, too.
So glad you love this, Shannon!
I’m very confused on the chocolate to use for the cake! Can you just tell me what brands I should use to make it easier? 1/4 cup of what brand, and 1/2 cup of what other brand. The only cocoa powder I have in my pantry is by Prepared Pantry and it says Groumet Ramstadt-Breda Dutch-Processed from Holland. Will that work? And if so, is that the 1/4 cup or the 1/2 cup? And then what would the other one be?
Hi DC Pear, we recommend a blend of unsweetened natural cocoa powder (1/4 cup; 22g) and a dutch-process cocoa powder (1/2 cup; 43g). So, you can use your dutch-process cocoa powder (1/2 cup) and then 1/4 cup of a natural cocoa powder. Any brand will work—we often use Hershey’s.
Thank you so much for the clarification!
Can the chocolate mousse recipe be used as a frosting instead of filling? Will it be stiff enough to hold its shape once refrigerated?
Hi Allison, many readers have reported success using the mousse for the outside of the cake. Let us know if you try it!
This looks delicious! Can I substitute olive oil or coconut oil for the vegetable oil?
Hi Heather, we recommend regular vegetable oil or canola oil for the most neutral taste. The others you mention will change the flavor of the cake a bit.
Probably the best cake iv ever made out of all ur recipes. Everyone loved itm fantastic
Can you make this cake the day before the event, and refrigerate overnight?
Hi Abigail! Refrigerate it overnight, and then, for best taste and texture, we would let it sit at room temperature for about 1 hour before serving.
Would it be possible to do a cream cheese mousse instead of chocolate? I want to make this for my daughter’s birthday, but worried it might be too chocolately for those who aren’t big chocolate fans.
Certainly!
Could you halve this recipe to make 2 round 8 or 9 inch pans as well as half the ganache and mousse ingredients?
Hi Corrie, yes, you can halve the recipe for a smaller cake.
Can I use a square pan instead of a round pan?
You should be able to use 8×8 pans here instead of 9 inch rounds.
Hi Sally I live in a little town in Brazil and there does not seem to be any sour cream availabe, do you think homemade would work just as well or yogurt?
Yogurt is a great substitute for sour cream.
Can you assemble and then freeze this cake?
Hi Abby, sure can! See recipe notes for make ahead and freezing instructions.
I read the through the freezing instructions and I wanted to clarify something. Would the cake be ok if I made it completely and then froze the whole cake fully assembled for a week? Trying to plan ahead for a birthday party where I won’t be able to make it day of or day before. Thank you!
Hi Lauren, Yes the frosted and assembled cake freezes well. Before serving, you’ll want to thaw the cake overnight in the refrigerator, then bring to room temperature or serve cold. Hope this helps!
Absolutely delicious! Surprisingly not too sweet. Beautiful cake & I will make this again.
Hi Sally,
Will overshipping the whipped cream into stiff peaks rather than soft/medium peaks before adding the chocolate cause the mousse not to set or become runny?
Hi Marguerite, we recommend whipping into medium peaks for best texture and ability to spread the mousse evenly on the cake. Avoid over-mixing to stiff peaks which can deflate/thin out the mousse.
can this one be cupcakes as well
Hi Joy, Sure can. See “What About Cupcakes?” section in the post for more details.