This super moist dark chocolate mousse cake combines unsweetened natural cocoa powder and dark cocoa powder for an extra rich flavor. Fill the cake with a simplified chocolate mousse and cover the whole dessert with semi-sweet chocolate ganache. If needed, you can prepare the ganache and mousse ahead of time.
Chocolate mousse is simple divinity in its own right, but when paired with chocolate cake, it’s downright decadent. And then add chocolate ganache to the mix? Have mercy.
This spectacularly rich chocolate cake is such a personal and reader favorite that I knew I had to include it in my cookbook, Sally’s Baking 101 (which has become a New York Times Best Seller!). The cakes chapter just would not have been complete without it!
It’s actually the first recipe in that chapter, and in the book it’s titled “Chocolate Ganache Cake: 2 Ways,” because I include a second filling option—peanut butter frosting instead of chocolate mousse, just like this recipe for dark chocolate peanut butter cake. Both versions of ganache-topped chocolate layer cakes have received such glowing reviews on my website, I simply couldn’t choose between them… so I found a way to include them both!
This cake basically demands a huge gathering because—trust me—you don’t want to be left alone with its temptation. It WILL call out your name each time you open the refrigerator.
Taunting you.
One reader, Judy, commented: “Don’t make this cake unless you want everyone who has a bite to request that you make it for every special occasion for the rest of time 🙂 I do four layers and follow the recipe exactly, and it has come out perfectly every time. I’ve already made at least ten of these cakes. Fabulous! ★★★★★“
One reader, Cecilia, commented: “OMG! This cake is absolutely divine! It’s a chocolate lover’s dream. The chocolate mousse is heavenly. I made it for my niece’s birthday and ended up making a four-layer cake. There were no leftovers. I don’t need any other chocolate cake recipe. This is it! Definitely the best! ★★★★★“
One reader, Brittney, commented: “This cake turned out amazing! I made it for a birthday party… and it was requested to be the new ‘party cake’! ★★★★★“
3 Parts to Dark Chocolate Mousse Cake
Let’s break down each component of this intensely rich cake:
- Dark Chocolate Cake: This is actually a variation of my tuxedo cake, which originated from my chocolate cake recipe. In recent years, I’ve found that replacing sour cream for some of the buttermilk gives the cake more structure.
- Chocolate Mousse: I researched simplified ways to make a fluffy chocolate mousse filling without the use of eggs or gelatin. This chocolate mousse filling combines real chocolate and homemade whipped cream. Or our whipped frosting would make a wonderful alternative filling if you don’t want to make the chocolate mousse!
- Chocolate Ganache: Top the whole cake with 2 ingredient semi-sweet chocolate ganache. You should be a chocolate ganache pro by now!
Video Tutorial: Chocolate Mousse Cake
Stick-to-the-back-of-your-fork moist. This is every chocolate lover’s dream!
Dark Chocolate Cake
Use this chocolate cake as the starting point. For a sturdier, yet moister crumb, swap some sour cream in for the buttermilk and reduce the hot liquid. The acidity in both sour cream and buttermilk is a must to properly leaven this cake. (If desired, see my posts on Baking Powder vs Baking Soda and Baking with Buttermilk for more information.) This cake has a natural dark chocolate taste, but to deepen that flavor, use a mix of natural cocoa and Hershey’s Special Dark cocoa powder. A touch of espresso powder and hot coffee further enhances the chocolate flavor. The cake will not taste like coffee. Rather, the two add depth to the cake’s chocolate flavor.
- Why hot liquid? The hot liquid encourages the cocoa powder to bloom and dissolve. If you don’t drink coffee, you can use hot water.
You have options! You can make this cake into 2, 3, or 4 layers. I highly recommend 3 or 4 layers because there’s over 4 cups of chocolate mousse to spread inside. You can use 8 inch or 9 inch pans. The bake times are similar, see recipe notes.
A cup of chocolate chips adds even more chocolate flavor. I used 1 cup (180g) of mini semi-sweet chocolate chips in this pictured cake, but left them out in the video. They’re optional, but definitely worth the addition!!
You can also see this exact cake batter baked as three layers in both my chocolate peanut butter cake and chocolate raspberry cake (try one of those next!).
Simplified Chocolate Mousse
The chocolate mousse adds a creamy and light contrast to the dark chocolate layers. You need 6 ingredients:
- Hot Water
- Cocoa Powder – natural or dutch-process
- Melted Chocolate – use two 4-ounce chocolate baking bars found in the baking aisle
- Heavy Cream
- Confectioners’ Sugar
- Vanilla Extract
Whisk the hot water and cocoa powder together. Pour into melted chocolate. The hot water breaks up the chocolate, adding to the airy mousse consistency. Cocoa powder creates additional chocolate flavor. Fold this chocolate mixture into whipped cream—a combination of heavy cream, confectioners’ sugar, and vanilla extract.
Whipped cream + our chocolate mixture. ↑
Fold them together to make our chocolate mousse filling. ↓
Baker’s Tip: The chocolate mousse must chill in the refrigerator before using, so it’s a good idea to make it ahead of time or as the chocolate cake layers are cooling. The mousse is best cold, so I actually recommend serving the cake cold. (Additionally, the cake is much easier to assemble if the mousse is cold!)
By the way, this chocolate mousse also makes for a wonderful alternate filling in homemade eclairs!
Chocolate Ganache
I won’t go into a lot of detail about the chocolate ganache because I have a complete chocolate ganache tutorial for you! Like the chocolate mousse, it’s imperative to use pure chocolate. Wait about 20 minutes for the ganache to thicken before pouring onto the cake.
How to Assemble & Decorate Chocolate Mousse Cake
Chocolate ganache enrobes 4 cake layers and 3 mousse layers. Place bottom cake layer on your cake stand or serving plate. Using a large icing spatula, evenly cover the top with about 1.5 cups of chilled chocolate mousse. Top with 2nd cake layer and another 1.5 cups of mousse. Top with the third cake layer, then spread another 1.5 cups mousse evenly on top. (Save a large spoonful of mousse for a thin crumb coat.) Top with final 4th cake layer. Spread any remaining mousse around the sides as a crumb coat. Run a bench scraper around the cake to smooth it out. Refrigerate cake for at least 1 hour and up to 4 hours. Chocolate mousse is pretty fluffy, so the cake won’t hold its shape unless it’s properly chilled.
Pour ganache on top then run a bench scraper around the sides to smooth it out. You can serve the cake immediately or wait for the chocolate ganache to set. 🙂
What About Cupcakes?
Instead of a big cake, you can make chocolate mousse cupcakes. Use my chocolate cupcakes recipe and halve the chocolate mousse and chocolate ganache recipes below. Fill the cupcakes with chocolate mousse using my Sugar Plum Fairy Cupcakes as an example. Drizzle cooled cupcakes with ganache. Eat your heart out!
You can also use the chocolate mousse instead of pastry cream in homemade mille-feuille!
More Indulgent Chocolate Desserts
- Dark Chocolate Bread Pudding
- German Chocolate Cake
- Flourless Chocolate Cake
- Black Forest Cake
- Chocolate Lava Cakes
- Chocolate Mousse Pie
- Mint Chocolate Cake
Dark Chocolate Mousse Cake
- Prep Time: 2 hours, 30 minutes (includes chilling)
- Cook Time: 25 minutes
- Total Time: 5 hours, 55 minutes (includes cooling)
- Yield: serves 12
- Category: Cake
- Method: Baking
- Cuisine: American
Description
This super moist dark chocolate cake combines unsweetened natural cocoa powder and dark cocoa powder for an extra rich flavor. Fill the cake with a simplified chocolate mousse and cover it with semi-sweet chocolate ganache. If needed, you can prepare the ganache and mousse ahead of time (see Notes). This recipe is also in my New York Times best-selling cookbook, Sally’s Baking 101.
Ingredients
- 1 and 3/4 cups (219g) all-purpose flour (spooned & leveled)
- 1 and 3/4 cups (350g) granulated sugar
- 3/4 cup (64g) unsweetened natural cocoa powder* (see Notes)
- 2 teaspoons espresso powder (optional)*
- 2 teaspoons baking soda
- 1 teaspoon baking powder
- 1 teaspoon salt
- 3/4 cup (180g) full-fat sour cream, at room temperature
- 1/2 cup (113g/120ml) vegetable oil
- 2 large eggs, at room temperature
- 1/2 cup (120g/ml) buttermilk, at room temperature*
- 2 teaspoons pure vanilla extract
- 1/2 cup (120g/ml) hot water or black coffee*
- 1 cup (170g) semi-sweet mini chocolate chips tossed in 1 Tbsp flour (optional)
Chocolate Mousse
- 1/2 cup (120g/ml) hot water
- 1/4 cup (21g) unsweetened natural or Dutch-process cocoa powder
- 8 ounces (226g) quality semi-sweet chocolate, finely chopped*
- 2 cups (480g/ml) heavy cream, cold
- 2 Tablespoons confectioners’ sugar
- 1/2 teaspoon pure vanilla extract
Chocolate Ganache
- 8 ounces (226g) quality semi-sweet chocolate, finely chopped
- 1 cup (240g/ml) heavy cream
- optional, for garnish: fresh berries and/or chocolate shavings
Instructions
- Preheat the oven to 350°F (177°C). Grease four 8-inch or 9-inch cake pans, line with parchment paper rounds, then grease the parchment paper. Parchment paper helps the cakes seamlessly release from the pans. (If it’s helpful, see this parchment paper rounds for cakes video & post.)
- Make the cake: In a large bowl, whisk the flour, sugar, cocoa powder, espresso powder, baking soda, baking powder, and salt together. Set aside.
- In another large bowl using a handheld or stand mixer fitted with a whisk attachment (or you can use a whisk) mix the sour cream, oil, and eggs together on medium-high speed until combined. Add the buttermilk and vanilla and mix until combined. Pour the dry ingredients into the wet ingredients, add the hot water/coffee, and whisk or beat on low speed until combined. Fold in the floured mini chocolate chips, if using. Divide the batter evenly among the prepared pans.
- Bake for 19–23 minutes. Baking times vary, so keep an eye on yours. The cakes are done when a toothpick inserted in the center comes out clean. Cool the cakes in the pans set on a cooling rack for 1 hour. Run a knife around the edges to help loosen the sides, remove the cakes from the pans, peel off the parchment, and place on the rack to finish cooling. The cakes may slightly sink in the middle as they cool—that’s expected.
- Make the chocolate mousse: In a small bowl, whisk the hot water and cocoa powder together until smooth. Melt the chopped chocolate in a double boiler or use the microwave. If using the microwave: place the chopped chocolate in a medium heat-proof bowl. Microwave for 20-second increments, stirring after each increment until completely melted and smooth. Pour hot water/cocoa mixture into the melted chocolate and stir until thick and smooth. Set aside. In a large bowl using a handheld or stand mixer fitted with a whisk attachment, whip the heavy cream, confectioners’ sugar, and vanilla extract together on medium-high speed until medium peaks form, about 3 minutes. Medium peaks are between soft/loose peaks and stiff peaks. Pour in the chocolate mixture and gently fold together with a spatula. Do not overmix, as this could deflate it. Cover the mousse and refrigerate for at least 2 hours or up to 2 days. Makes about 4.5 cups (about 900g).
- Assemble the cake before preparing chocolate ganache: First, level the cakes (if needed): using a large serrated knife, slice a thin layer off the tops of the cakes to create a flat surface. Place 1 cake layer on your cake stand, cake turntable, or serving plate. Using a large icing spatula, evenly cover the top with about 1.5 cups (200g) of chocolate mousse. Top with the second layer, upside down, and evenly cover the top with the same amount of chocolate mousse. Top with the third cake layer, right side up, and again cover with the same amount of mousse. Top with final cake layer. Spread the remaining mousse on top and around the sides of the cake as a crumb coat. Run a bench scraper around the cake to smooth out the sides. Refrigerate for at least 1 hour and up to 4 hours. Prepare the ganache while the cake is chilling.
- Make the chocolate ganache: Place the chocolate in a medium heat-proof bowl. In a small saucepan, heat the cream over medium heat just until it begins to gently simmer. (Do not let it come to a rapid boil—that’s too hot!) Pour the warm cream over the chocolate and let it sit for 2–3 minutes to gently soften the chocolate. With a metal spoon or small spatula, slowly stir until the chocolate has melted and the mixture is smooth. The finer you chopped the chocolate, the quicker it will melt with the cream. If it’s not melting, do not microwave it. If needed, see Troubleshooting Chocolate Ganache. Refrigerate the ganache for at least 30 minutes or up to 1 hour to thicken.
- Pour/spoon the thickened ganache on the chilled cake. Smooth the top and sides with an icing spatula. Top with optional garnish such as fresh berries and/or chocolate shavings. Serve cake immediately or chill, uncovered, for up to 4–6 hours before serving. Cake can be served at room temperature or chilled.
- Cover leftover cake tightly and store in the refrigerator for up to 5 days.
Notes
- Make Ahead & Freezing Instructions: Prepare cake through step 4. Wrap the individual baked and cooled cake layers tightly and refrigerate for up to 2 days or freeze up to 3 months. Bring to room temperature, make mousse filling, then continue with step 6. You can prepare the chocolate mousse in advance. See step 5. You can also prepare the chocolate ganache ahead of time too. Refrigerate prepared ganache for up to 3 days. Bring to room temperature before spreading onto cake. You can freeze cake for up to 3 months. Thaw overnight in the refrigerator, then bring to room temperature or serve cold. See How to Freeze Cakes for more information.
- Special Tools (affiliate links): 8-inch Round Cake Pans or 9-inch Round Cake Pans | Glass Mixing Bowl | Whisk | Electric Mixer (Handheld or Stand) | Cooling Rack | Double Boiler | Cake Stand or Cake Turntable | Large Icing Spatula | Bench Scraper | Cake Carrier (for storage)
- 3-Layer Cake: You can also prepare this as a 3-layer cake. Divide batter between three 8-inch or 9-inch cake pans in step 1 and bake for 24–26 minutes or until a toothpick inserted in the center comes out clean. Use about 2 cups of chocolate mousse between each layer.
- Espresso Powder/Coffee: Espresso powder and coffee will not make the cake taste like coffee. Rather, they deepen the chocolate flavor. I highly recommend them both. You can find espresso powder in the baking aisle at many grocery stores or online. If coffee isn’t your thing, you can leave out the espresso powder and use hot water instead of the hot coffee.
- Cocoa Powder: For the best dark chocolate flavor in the cake, I recommend using a blend of unsweetened natural cocoa powder (1/4 cup; 21g) and Hershey’s “Special Dark” cocoa powder (1/2 cup; 43g). Hershey’s Special Dark is actually a mix of natural cocoa powder (an acid) and Dutch-process cocoa powder (a base) and it worked fine in this recipe. This recipe needs acidic natural cocoa powder, so do not use ALL Dutch-process cocoa powder. For best results, use 3/4 cup (64g) natural or the blend of natural/Special Dark I used. For the chocolate mousse, you can use either unsweetened natural or Dutch-process cocoa powder (or the Hershey’s Special Dark).
- Why Room Temperature? All refrigerated items should be at room temperature so the batter mixes together easily and evenly. Read more about why room-temperature ingredients are important. Instead of sour cream, you can use plain yogurt. The cake won’t taste as rich, but it’s a fine substitute.
- Buttermilk: Buttermilk is required for this recipe. You can make your own DIY buttermilk substitute if needed. Add 1 teaspoon of white vinegar or lemon juice to a liquid measuring cup. Then add enough whole milk to the same measuring cup until it reaches 1/2 cup. (In a pinch, lower-fat or nondairy milks work for this soured milk, but the cake won’t taste as moist or rich.) Stir it around and let sit for 5 minutes. The homemade “buttermilk” will be somewhat curdled and ready to use in the recipe.
- Chocolate in Mousse & Ganache: Mousse & ganache will only set if the correct chocolate is used. You can use high-quality chocolate chips if needed (I prefer Ghirardelli semi-sweet chocolate chips), but I recommend using pure chocolate baking bars. You can find them right next to the chocolate chips in the baking aisle. They are sold in 4-ounce (113g) bars. I like Baker’s or Ghirardelli brands.
Reader Comments and Reviews
I’ve made this cake several times and everyone loves it. It’s super easy to make. Question, this time I’m making it 4 days ahead of time. Should I freeze it or is it safe in the frig? Thanks!
Hi Cathy, so glad you love this cake! See Notes after the recipe for our recommended make-ahead instructions. We would freeze the cake!
Can I use gluten free flour instead of normal flour? Has this been tried?
Hi Trisha, we haven’t tested a gluten free version of this cake, but let us know if you do!
Sally can I double this recipe?
Hi Kate, We recommend making two batches of batter instead of doubling.
Hi! I only have 2 8” rounds cake pans… how would that change cooking time/outcome ? Do I need to slice them in half?
Hi Kathleen, you can bake half of the batter in 2 pans and bake the next 2 after.
The cake is great! But I recommend starting with the mousse so it will be ready to assemble the cake when the cake is ready. Also, my ganache was too hard after 30 minutes. Next time, I will keep it in the fridge for 15 minutes only.
Am I missing something? I got Sally’s Baking 101 for my birthday this month but I cannot find this recipe in it. Obviously I can use this online version but I much prefer using a cookbook
Hi Sally, see page 81!
Thank you. I did see that but different name and only three layers vs four online so I thought it was a whole different recipe. I’ll try it!!
I made this cake for my Dad’s 95th birthday. He loved as did everyone who had a slice. It is RICH, so a little goes a long way. Since it needs some planning, and I don’t always have a huge amount of time, it worked well to make the bases on one day (froze them). Then the mouse the second day. On the third day, I unfroze the bases, covered them with the layers of mouse, made the ganache and finished the cake. Then it went into the fridge, and was ready and served on the fourth day (birthday) topped with some fresh berries. Worth the effort!!
Hi Sally, I made this as a trial the night before fully assembled and served next evening and it was great. I’m hoping it was not beginners luck. I love the cake and want to make it again for my friend but do not have the band width to do the whole thing day of party as I have a lot of cooking to do. What would you suggest is the best make ahead way? I would be finishing it with the ganache night before and serving it chilled the next night. If theres a better way of making ahead pls lmk. thank you!
Hi Karen, see our recommended make-ahead instructions in the Notes after the recipe! Glad you love this cake.
Thanks Trina! I did read that. More from freezing than preparing and refrigerating ahead when it’s all done. Would you say that’s ok too?
Hi Karen, that should be ok!
Hey Sally. The mousse had a weird appearance. Didn’t dissolve completely in the cream. Any idea why? Tasted great but looked bad. lol. Followed ur recipe to a T. Appreciate any tips. Thanks!
Best cake I’ve ever made!!! I added subbed almond extract and added some maraschino cherry juice and chopped cherries to the mousse for a cherry-amaretto twist, it turned out great! Vanilla ice cream was a win too 😉 Thanks so much for all your recipes Sally!
Hello,
I’m curious to know if this batter can be baked in two 8″ or 9″ square pans to make 1 double layer square cake instead.
Hi Sophie! Here is everything you need to know about converting recipes to different Cake Pan Sizes.
Hi! How long would this last served at room temperature? Thanks!
Hi Cine, the cake will be fine at room temperature for a few hours. If you can refrigerate it beforehand, that would be great.
Is there an alternative to hersheys special dark bc it appears to be a shortage
Hi Grace, any unsweetened natural cocoa powder will work perfectly here!
Can I use black cocoa to sub the hersheys dark? I’ve only ever used the suggested proportions and using only unsweetened makes me concerned it won’t come out as rich?!?
What substitute can we use for sour cream?
Plain yogurt works well!
Hi Sally I have a question about the mousse. I will be making it 1 or 2 days prior to assembling the cake. Should I need to rewhip the mousse before putting it on the cake, or will it be ok straight from the fridge?
Hi Sue! The mousse can be made ahead of time – refrigerate for at least 2 hours or up to 2 days. No need to re-whip.
Great. Thank you!
Will reduced fat yogurt or sour cream work ok? That’s all I have
yes it would!!!
Could this be made as a 13 x 9 cake? I want to make a dark chocolate cake but use a different frosting recipe on your site. Thank you!
Hi JoJo, You can make this recipe as a 9×13-inch sheet cake (same oven temperature, about 35-40 minutes bake time). Enjoy!
Can the ganache be made with white bakers chocolate?
Hi Rosemary, absolutely. See our chocolate ganache post for details on using white chocolate. If using white chocolate, reduce the cream to 2/3 cup (160ml). White chocolate is softer, so you need less cream.
I’ve made this cake a number times over the past few years for my son and he just requested it again for Valentine’s Day again. I follow the recipe to the letter and it comes out amazing every time! I follow her notes to make 3 layers instead of 4. Sally’s recipes never fail me 🙂
Hi, I made this cake for my family for Valentine’s Day and it was pretty good! I was admittedly a little frazzled and rushed because I still had some work to do but I got it done and was pretty satisfied with it. I didn’t realize I had 9 inch pans instead of 8 inch until it was too late, and I only made two layers, but I tried to otherwise follow the recipe to a T. My one slight issue is that once I sliced into that bad boy my cake wasn’t as dense looking as in your pictures, it was airy and the crumb looked kind of “spread apart” for lack of a better term. I could’ve sworn I mixed it only until it was combined but i don’t know. There were also small air bubbles in the batter. Did I do something wrong or is this normal? The cake was still good btw, it was pretty moist and soft, even though the edges were more crispy and crumby.
I’ve made this cake many times and will be making for a friends birthday; I have to transport the cake would you recommend adding gelatinous to the mousse for more stability? Thanks
Hi Kat, If the cake is kept chilled during the drive it should be ok.
Hi CazT, we haven’t tested a gluten free version of this cake, but let us know if you do!
OK – it might be risky but I think I’ll try it!
This cake was amazing! Turned out exactly as pictured. Well worth the effort.
Will this filling hold up in a large cake (12”, 4 layers?)
Hi Lisa, that shouldn’t be a problem. You may want to use cake dowels for a bit of extra support. We hope you enjoy the cake!
Hi, I only have cake flour. Can I use that instead of AP?
Hi Arsh, All purpose flour is best for this cake. 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.
Hi! I’m making this cake for the first time and was wondering how many calories per serving it is. Thank you!!
Hi Taylor, 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
I’ve made this cake several times and I’ve gotten only rave reviews. It’s a cake no one will forget. I’ve covered the outside with a Swiss meringue buttercream(another Sally recipe)! It’s is absolutely delicious
Would this recipe work well with your raspberry cake filling and no chocolate ganache on the outside?
Hi Em, that shouldn’t be a problem. You’ll want to create a dam of mousse or frosting around the edges of the cake layers to prevent the cake filling from coming out the sides.