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.
My s’mores chocolate mousse inspired me to play around in the kitchen the other week. I’ve always loved chocolate mousse, back to my childhood when my mom served it as an easy (yet totally elegant) dessert on the holiday table. Chocolate mousse is simple divinity in its own right, but when paired with chocolate cake, it’s downright decadent.
I made this chocolate mousse cake for my husband Kevin’s birthday. 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.
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 baking powder vs baking soda 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!)
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.
Ingredients
- 1 and 3/4 cups (219g) all-purpose flour (spooned & leveled)
- 3/4 cup (62g) unsweetened natural cocoa powder* (see note)
- 1 and 3/4 cups (350g) granulated sugar
- 2 teaspoons baking soda
- 1 teaspoon baking powder
- 1 teaspoon salt
- 2 teaspoons espresso powder (optional)*
- 1/2 cup (120ml) canola or vegetable oil
- 2 large eggs, at room temperature
- 3/4 cup (180g) full fat sour cream, at room temperature
- 1/2 cup (120ml) buttermilk, at room temperature*
- 2 teaspoons pure vanilla extract
- 1/2 cup (120ml) hot water or coffee*
- optional: 1 cup (180g) mini or regular semi-sweet chocolate chips
- optional garnish: fresh berries and/or chocolate shavings
Chocolate Mousse
- 1/2 cup (120ml) hot water
- 1/4 cup (22g) unsweetened cocoa powder* (see note)
- two 4-ounce quality semi-sweet chocolate bars (113g each), finely chopped*
- 2 cups (480ml) heavy cream or heavy whipping cream
- 2 Tablespoons (15g) confectioners’ sugar
- 1/2 teaspoon pure vanilla extract
Chocolate Ganache
- two 4-ounce quality semi-sweet chocolate bars (113g each), finely chopped*
- 1 cup (240ml) heavy cream or heavy whipping cream
Instructions
- Preheat 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: Whisk the flour, cocoa powder, sugar, baking soda, baking powder, salt, and espresso powder (if using) together in a large bowl. Set aside. Using a handheld or stand mixer fitted with a whisk attachment (or you can use a whisk) mix the oil, eggs, and sour cream together on medium-high speed until combined. Add the buttermilk and vanilla and mix until combined. Pour the wet ingredients into the dry ingredients, add the hot water/coffee, and whisk or beat on low speed until the batter is completely combined. Fold in the chocolate chips, if using.
- Divide batter evenly between 4 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.
- Remove the cakes from the oven and set on a wire rack. Allow to cool completely in the pan. The cakes may slightly sink in the middle as they cool—that’s expected.
- As the cakes cool, prepare the chocolate mousse so it can chill and be ready at the same time as the cake layers. You can also prepare the mousse 1-2 days ahead of time. Whisk the hot water and cocoa powder together. Set aside. Melt the chopped chocolate bars in a double boiler or use the microwave. If using the microwave: place the chopped chocolate in a medium heat-proof bowl. Melt in 20 second increments in the microwave, stirring after each increment until completely melted and smooth. Pour hot water/cocoa mixture into melted chocolate and stir until thick and smooth. Set aside. Using a hand mixer or a 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 3-4 minutes. Medium peaks are between soft/loose peaks and stiff peaks. Pour in the chocolate mixture and using a spoon or rubber spatula, gently fold together. Avoid over-mixing which can deflate/thin out the mousse. Cover mousse and chill in the refrigerator for at least 2 hours and up to 2 days. Makes about 4.5 cups chocolate mousse.
- Assemble layers 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. Discard (or crumble over ice cream!). 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 chocolate mousse. Top with 2nd layer and evenly cover the top with 1.5 cups chocolate 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 out crumb coat. Refrigerate cake for at least 1 hour and up to 4 hours. Prepare the ganache as you wait.
- Chocolate Ganache: Place chopped chocolate in a medium heat-proof bowl. Heat the cream in a small saucepan over medium heat until it begins to gently simmer. (Do not let it come to a rapid boil– that’s too hot!) Pour over chocolate, then let it sit for 2-3 minutes to gently soften the chocolate. With a metal spoon or small rubber spatula, very slowly stir until chocolate has melted and 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. Once ganache mixture is smooth, let it cool for 20 minutes at room temperature before spreading on chilled cake.
- Pour/spoon ganache on chilled cake. Smooth the top with an icing spatula and the sides with a bench scraper. 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 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 2-3 days. Bring to room temperature before spreading onto cake. Frosted cake freezes well, up to 3 months. Thaw overnight in the refrigerator, then bring to room temperature or serve cold.
- 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 cake as a 3 layer cake. Divide batter between three 8-inch or 9-inch cake pans in step 1 and bake for 22-25 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. If coffee isn’t your thing, you can leave out the espresso powder and use extra 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; 22g) 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 (65g) 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 version of buttermilk 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 bars. I like Bakers or Ghirardelli brands.
Hi. I made this cake twice already. I love it. Can I use the same thing to make a Swiss roll? I like everything but the chocolate garnarsh is too much work and too much chocolate for me. Thus I think a Swiss roll version would be great.
Hi Susana, I’m so happy you love this cake! For a Swiss roll I recommend using my Chocolate Cake Roll (Swiss Roll) recipe.
I made this cake for my birthday, it’s my new favorite cake. I made it a 3 layer cake it was tall. I did get to share it with 2 of my son’s and family not getting to close to any of them. My oldest son and grandchildren brought me a lemon cake they took home a giant slice of my cake. Granddaughters said I need to make it again they loved it. When we all can be together and my Dad can come to town I will make it again with my 12 inch cake pans, only 2 layers. Each layer takes 1 1/2 recipes. need a large cake for 15 people with some leftovers.
This is my favorite chocolate cake! It was incredible! I also like that it doesn’t have buttercream, because that makes it easier to ice.
Hi Sally. I made chocolate mousse today using Semi sweet Ghirardelli baking bars, Hershey’s cocoa powder and heavy cream. Whipping cream was medium peaks but when I poured the melted chocolate+hot cocoa mixture to it, it became watery when compared to what I saw in your video. Should I make another batch of it or is there a way to fix it?
Chilling it should help re-solidify it. Were you sure to use heavy cream/heavy whipping cream? (Simply “whipping cream” contains less fat and I don’t recommend it.)
Thanks Sally for the quick response. I did use heavy whipping cream. It did solidify after I put it in the fridge. But when I am assembling the cake should I let the mousse cool down to room temperature? May be it will become watery with temperature difference?
My cake came out amazing a few days ago! Big hit! I plan on making this again for an anniversary. What would the baking time be if I use (4) 10X2 pans? Will I have enough batter? Should I use (3) instead? Thank you!
Hi Seth, I’m so glad you enjoyed this cake! There isn’t enough batter here for four 10-inch pans. You can see my post on Cake Pan Sizes and Conversions to help you figure out how much batter you would need.
Hi Sally,
Love love the recipe. Cake is the just perfect but only one think it turned out bit salty , I am guessing from the taste its from baking soda. I used everything as per the recipe.
Thankyou
Oh wow was this good! Due to so many bakeries and stores have been shut and I couldn’t get my son a birthday cake. We made this cake and then piped your butter cream frosting to decorate it. Was worried the flavors would clash but it was amazing. I don’t really like cake (weird I know) but this was amazing! Better than bakery cakes! I accidentally only bought 2 bars of bakers chocolate instead of 4 so I used one and chocolate chips for the mousse and ganache and luckily it worked perfectly. We already have plans to make this cake with raspberries on top or use the mousse in something else! Thanks for your easy to follow recipes!
I’m not a baker at all and this was the first cake I’ve made, let alone from scratch. The recipe was easy enough to follow and yielded great results! As a new baker I baked 3 layered chocolate cake filled with ganache and frosted with whipped ganache. I made this for Easter Sunday and it was a hit! As a chocolate lover, this was the best chocolate cake I’ve ever had. Thank you Sally!
Thanks for answering so fast! We just had this delicious cake for my dads birthday and I’d just like to say, WOW your amazing! I’m in awe about what is sitting in front of me! This is my first non-falling apart cake and my dad loved it! It’s better then any chocolate cake I’ve ever had and my dad agrees! Thank you so much for this recipe and for answering my comments and questions!
Hi! I’d like to make a mocha mousse for this cake (in the same vein as the mocha whipped cream from your flourless chocolate cake recipe). Do I just add a teaspoon of espresso powder to the mousse ingredients? Or does anything else need to be adjusted?
Also, do you get the espresso powder from the baking aisle, or is it just straight ground espresso from the coffee aisle?
Hi Crystal, you can add espresso powder to the mousse for a little coffee flavor. You can usually find it in the coffee aisle.
Hope you are safe and well. I am planning to bake the cake tomorrow, one day ahead… I couldnt find buttermilk at my grocery store, may I replace it with almond milk? If so, would it be still fine to leave it in the fridge oVernight?
Hi Nancy, in a pinch, you can use nondairy milk as the DIY buttermilk substitute described in the recipe note.
This recipe looks amazing! I’ll be making this in a few days. Question, do you use conventional bake for all 4 pans? I’ve never baked more than 2 pans at once…I know placement in the oven is crucial.
Hi Seth, I do use the conventional setting on my oven for all of my baked goods. If you can’t fit all 4 pans on one rack in your oven you can place them on different racks and rotate half way through. Likewise, if you know your oven has hotspots you can rotate the position of the pans part way through baking. Enjoy the cake!
Made this recipe today and it was delicious. The cake is moist and the mouse is decadent. The only thing that would have made the recipe better would have been to list the weight of the batter in each if the four pans.
Hello. I’ve never baked a cake before but my sons bday is two days away and we are on lockdown so I want to give this great sounding recipe a try. My question is, I have a 4 pack of rectangular pans that are 10 inch x 4 in x 3/4 inch deep. Are the pans too small for this recipe? Thanks
Hi Don, this batter could likely fit in two of those pans but I recommend using my Cake Pan Sizes and Conversions post to determine the best substitution.
Hi I was bored being locked down and found your recipe. I didn’t have strawberries to decorate but trust me the cake came out so well and the family is enjoying it. Thanks for sharing your recipes. Appreciate it.
great recipe. It was a hit and the birthday girl loved it!
Hi Sally
I am planning to make this cake for my wife’s birthday in few days. trouble is i only have one cake baking tray. Someone above in the comments suggested pouring all batter in the tray and then cutting it when ready and you said it is not a good idea. Is it ok if i bake each layer one after another. what will happen to the batter if you leave it for long period of time (4th layer will be baked 2-2.5 hours after everything is mixed together). would that affect the sponges?
Many thanks
Hi Peter, I’m happy to help. You can let the unused batter sit at room temperature, covered, until the cake pan is ready to use again. Baking right away would be ideal for the cake’s texture, but this is the only way if you only have 1 pan.
Hi Sally! I would like to use this recipe but use a chocolate cake instead of this dark chocolate cake. Will the mousse and ganache taste good with a standard chocolate cake?
Yes, they would still be delicious!
Hi! I was thinking of using the chocolate mousse to do a crumb coat for a “naked cake” effect and then using the ganache to do a chocolate drip rather than coating the cake in the ganache. Do you think this would work well, or should I use icing rather than the mousse to created the naked look?
Hi Hannah, The mousse will work for this. Enjoy!
It’s was soo good my kids loved it and it was so easy to make
One of the best cakes I’ve ever made. Made this for my dad’s 60th. He was very impressed and it tasted amazing. Everything about it is great. Substituted the espresso powder for Green and Black’s cocoa powder and the coffee for Earl Grey tea – not a coffee person! Homemade buttermilk (not that common in UK). Unbelievably scrumptious! Every aspect was superb. Thanks a lot!
Oh my how you inspire me! I made this cake yesterday, I bake something for the office every week, and try so many of your recipes! This cake is sooooo good. I have made and had good cake before, but this is a whole other level of creamy chocolatey goodness. Thank you for sharing this one!
I loved it. I have finally found my go to chocolate cake receipe. So moist and delicious. I need to however work on my presentation skills. My mousse came out a little soft but thats because I was scared to over whip it.
I am planning to assemble the cake (cake and mousse) and refrigerate it overnight. The next day I will be making the ganache and pouring over the cake. My question is, should I pour the ganache over refrigerated cake or room-temperature cake. My concern is that since the heavy cream will be warm, it will “melt” the cake. Thanks!
Hi Carolina, I always recommend pouring the ganache over a cold cake. Additionally you should let your ganache sit at room temperature for about 20 minutes to cool down so it won’t be super hot when it’s poured over the cake Enjoy!
Hi Sally….was wondering if this cake would hold under fondant
Shouldn’t be a problem!
I want to use this to make tea cakes/petit fours. To make it sturdier, should I replace all the buttermilk with sour cream, or just part of the buttermilk? I noticed it already calls for some sour cream. How much should I reduce the hot coffee by?
Hi Megan! You can try replacing all of the buttermilk with extra sour cream to make a denser cake. No need to replace or reduce the hot liquid.
I made this cake for my birthday. It was absolutely delicious!!! I just made the mousse as the icing, and covered with berries. Super rich, chocolately and simple to make. Best chocolate cake I have made!
Sally-
Thank you for such an outstanding recipe and thorough directions. I made the cake for Christmas Eve dinner and everyone loved it!!! I will definitely be making it again….I find myself longing for a piece on a daily basis – haha!
Mary
Hi Sally,
I have only one egg to use, can I substitute anything else for the other egg?
Thankyou
Hi Sally,
Am I able to use this recipe for cupcakes? Or is the cake so moist that it will have trouble sticking to the liners?
Hi Tori, I recommend using my chocolate cupcakes recipe and halve the chocolate mousse and chocolate ganache recipes. See the paragraph above called “What about Cupcakes?” for the full directions!