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
So delicious! My husband has requested every birthday for years!
Please clarify.
In the recipe online “Sally’s Baking,” it recommends to make this cake as a 4 layer cake either using 8 or 9 inch round pans. In my Sally’s Baking 101 book it states to use 3-9 inch round cake pans. Which is better?
Thank you.
Hi Camille! Correct, they are the same recipe. This online version splits the batter into 4 pans for thinner layers. The book splits the batter into 3 pans for slightly thicker layers. You can do whichever you prefer!
This cake was a hit! Delicious!!! I am from Australia and the ganache seemed to be more than I needed not sure what happened there but Delicious none the less
What can I use for dairy free buttermilk
Hi Carol, you could use a dairy-free milk to make a DIY buttermilk substitute. See recipe Notes for more details.
Disappointing. The mousse set, however, it kept getting too soft while applying. The cake kept sliding over & it was a hot mess. I kept putting it in the fridge & freezer, but the cake slid & the mousse oozed out the sides. I am so upset at how horrible it looks. No matter what I did I couldn’t salvage it.
Hi Debbie, I’m so sorry to hear this! How long did you refrigerate the mousse before layering it with the cake? And were your cake layers completely cool before assembling?
I read some positive reviews, so made this. Followed the recipe but the mousse did not set up. It was one sloppy mess. I should have guessed that 1/2 cup of water without thickener would not stay firm, even after/with refrigeration.
I had the same issue.
This is truly the best chocolate cake ever. I’ve made it many times and also receive rave reviews. Made it once with a strawberry mousse instead of chocolate and that was delicious too!
This was absolutely the best chocolate mousse cake I’ve ever tasted. Made it for a family dinner and everyone kept saying how amazing it was. It will definitely become my only chocolate mousse cake recipe that I will make. Thank you so much for sharing it.
What can I substitute for sour cream
Hi Lisa, typically, plain yogurt or Greek yogurt is a fine substitute for sour cream in baking.
Thanks you!!
One spot in the recipe calls for 8 ounces of baking chocolate in the mousse another spot calls for semi sweet. Which is it?
Hi Sheryl, the mousse recipe calls for pure baking chocolate. We use semi-sweet pure baking chocolate. See recipe Notes for more details.
Hi,
Love this cake! If I make in a 13X9, can I save the uncooked batter by freezing?
Hi Katie! Cake batter should be made and baked fresh. Baked cakes freeze well, though!
Hello! Wondering if you have any suggestions for replacing the eggs in the recipe. My daughter has an egg allergy and asked for a chocolate blueberry cake for her birthday perhaps more each of the sour cream and buttermilk?
Hi Sara, we haven’t tested this cake with any egg substitutes, but let us know if you do any experimenting. We don’t have much experience with egg substitutes. We hope whatever you try is a hit for your daughter’s birthday.
Hi, can I cut the ingredients in half to make a two layer cake instead of 4?
Hi AG, you could, it would be quite thin.
Can I freeze the mousse in silicone molds (possibly also putting a small filling of caramel in the mousse)? Want to use this mousse to create small, individual desserts. Thanks!
Hi Laurie, we haven’t tested that but can’t see why not – let us know if you try! We also have this s’mores chocolate mousse cups recipe you can reference.
Looks delicious. Can this be made as cupcakes?
Hi Gabriella, see the section of the blog post above titled “What About Cupcakes?” for details!
Can I bake this in square tins.
Hi Sandra, yes, you can bake in square pans instead. Here’s everything you need to know about cake pan sizes and conversions.
Sally, I want to make this for my mom’s birthday this weekend. But she’s allergic to sour cream. Can I swap it for yogurt? I’m also in high altitude CO I saw a person comment halving the leavening ingredients. What do you recommend?
Hi Madie! Plain yogurt will work in place of the sour cream. We have no experience baking at high altitude, but some readers have found this chart helpful: https://www.kingarthurflour.com/learn/high-altitude-baking.html Hope you enjoy this cake!
Sally,
Can you tell me why you recommend the assembled cake only chilling for 4 hours? This year, we’ll be hosting my son’s birthday directly after church and I’d love to make and decorate the entire cake the evening before.
Hi Larissa, you can chill for longer, but we’d recommend covering the cake (we like to use a cake carrier for this) if chilling overnight.
This is a great recipe. I make it every year for both my daughter’s and my birthdays.
A tip if you’re at higher altitude: the cakes cave in a little if you don’t reduce the leavening powders. I’m at about 5000 ft above sea level, and halving the powders works perfectly for me.
I have made this cake many times and it is absolutely the BEST! I am hoping to make it for my girlfriend who has celiac. Any advice on how to make it gluten free? Measurements for gluten free flours?
Hi Margaret, we haven’t tested this cake using an all-purpose gluten free flour, so we’re unsure of the results. Let us know if you do give it a try.
I cannot find Hersheys Special Dark cocoa near me -can I use C’Ote D’Azure black cocoa in its place
Hi Mary, see Notes after the recipe for details on the cocoa powder needed for this cake!
This recipe is phenomenal. My daughter asked for chocolate layers with chocolate mousse for her birthday. It was a small party, so I made half of the cake recipe, half of the mousse, and skipped the ganache. It layered and set up perfectly and served six with plenty left over. Worked super well to divide the recipe in half and it was incredibly delicious….exactly what my daughter wanted too. Really appreciate how simple and straight forward the recipe is, no unusual ingredients or tricky steps.
This is perhaps the most delectable and delightful dessert I’ve ever had. I don’t say that lightly. It is the only thing my husband asks for as his birthday gift every year. It is a masterpiece in texture and taste, and I am so proud to bake a cake at this level. I leave off the ganache because it takes me long enough to make as is ^_^ and I don’t think it’s needed, since the mousse shines on its own. I top it with fresh raspberries. Thanks so much Sally!
Hi!
I am in the process of making this amazing looking cake. Could you tell me how much gelatin I would use if I wanted more structure? I assume I would put it the water, just to bloom? Or using hot water?
Thank you,
Shelli
Hi Shelli! We haven’t tried adding gelatin to this mousse but you can certainly try if you wish.
I had people that do not like chocolate cake, tell me they love this one. It was delicious and so much better than chocolate buttercream! Easy to make and stunning to see, it’s an all around winner.
We love this recipe! How would I adjust to use milk chocolate for the ganache? What milk chocolate would you advise using?
Hi Chloe! You could use milk chocolate – just be sure that they are still pure baking chocolate bars.
This is one of my all-time favourite recipes, but I’m hoping to make it for a coffee lover – any suggestions for how to make this explicitly coffee flavoured, perhaps the mousse? Thanks!
Hi team! Do you have any ideas on how I could make this cake coffee flavoured as well as chocolate? Thanks!
Hi Kay! You can add espresso powder to the mousse to make a mocha mousse. We’d start with 1/2 teaspoon and adjust there for your liking. Enjoy!
I don’t really understand the make ahead of instructions. Are you saying you can assemble the whole cake and freeze it for up to three months? How long can I assemble the whole cake and refrigerate it for?
Hi Annabelle, you can freeze the assembled cake for up to 3 months, but you can also just assemble and refrigerate a day or so before serving, too.
Why do you prefer to not use gelatin in the mousse for structure?
Hi Chris, we don’t find it necessary for this particular recipe, but you could certainly add a bit if you’re looking for something with more structure. Let us know if you try it!
This was SO delicious and the instructions/recipe were easy to follow. The changes I made to the recipe were: I left out the chocolate chips (family preference), baked the cake as a 2 layer (only had 2 pans, just baked longer) and ran out of chocolate so only did about 60% of the ganache recipe. Cake was literally perfect still!! Thank you Sally for ALWAYS putting out the best recipes.
SO GOOD!!!
My son made this cake for his birthday. It’s beautiful. I’m just wondering what the calorific and micronutrients are. I’m used to UK recipes showing this as it helps me keep within the healthy range for an adult.
We don’t usually include nutrition information as it can vary between different brands of the same ingredients. Plus, many recipes have ingredient substitutions or optional ingredients listed. However, there are many handy online calculators where you can plug in and customize your exact ingredients/brands. Readers have found this one especially helpful: https://www.verywellfit.com/recipe-nutrition-analyzer-4157076
Hello, I gave not made this yet. Why does it look like peanut butter frosting in the pictures?
Hi Joyce, are you referring to the chocolate mousse filling? It’s a lighter brown color.