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!
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 (spoon & 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 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.
- 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.
Keywords: cake, chocolate mousse, dark chocolate
Hi! I see notes that these can be cupcakes. But just to be clear, can the mousse itself be piped as a light frosting, and then be topped with ganache? Or can the mousse only fill the cupcakes?
Hi Samantha, you can fill the cupcakes with the chocolate mousse. If you have any leftover (you will), you can also pipe some on top of the cupcakes.
Hi Sally, this looks so moist and rich. I want to use this as one of the tiers in a 3-tier cake. I am worried the mousse filling might not be able to withstand the weight, or other cakes may need to be softened before serving. Do you have a suggestion? Thanks!
Hi Nomchin, we don’t have a chocolate cake recipe sturdy enough to be the bottom of a tiered cake at this time. It could work as a top tier, though! You can reference our cake pan sizes and conversions guide to adjust this recipe.
Can I make this less sweet by lowering the sugar amount by 25% or does that mess with the recipe?
Hi Leena, You can try reducing the sugar, but keep in mind that sugar plays an important role in the taste, texture, and structure of a recipe, so we’re unsure of the results when using less sugar. We’d recommend starting small, and then you can reduce further in future cakes as needed.
Is there anyway that I could incorporate black cocoa in this recipe? What would you think the ratios would be of unsweetened cocoa to black cocoa? Just for the cake portion.
Hi Jennifer! 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.
Can you use lowfat buttermilk? I am making this on Saturday for my daughter’s 21st Birthday.
Hi Catherine, lowfat buttermilk will work in a pinch, but the cake won’t taste as moist or rich. Hope it’s a hit!
I have tired quite a few chocolate cakes recipes. This is absolutely my favorite! So moist and rich! Just so delicious thanks for the awesome recipe!
Can I use this recipe for cupcakes? Need to alter anything and baking time?
★★★★★
Hi Emi, you can certainly use this recipe for cupcakes — it will yield about 3 dozen. You can follow the bake time instructions from chocolate cupcakes as a guide. Or, simply use that recipe for a smaller yield and the directions from this post in the section titled “How About Cupcakes?” So glad this is a favorite for you!
Just one word…. Heavenly!
Thank you, Sally, for the amazing recipe and great instruction. I have never made chocolate mousse before so I was a little nervous. But your instruction and video were super helpful and it came out great! Now I can use this mousse recipe in other things too!
★★★★★
Just super delicious decadent 3 layer chocolate cake! Wonderful mousse.
I used your chocolate buttercream frosting . . My guests were thrilled. Thank you Sally. Again!
Have used so many of your recipes and they are always excellent
★★★★★
Amazing cake with easy to follow instructions. This has been requested for numerous family member’s birthdays and always turns out great. I have made with and without chocolate chips and it is great either way. Also, works great as a three layer instead of four if you don’t have four cake pans.
★★★★★
Can I divide the batter into two 9 inch pans, bake it and once it cools, slice them both horizontally to make the 4 layers? Will it affect the integrity of the cake? Or better use 4 pans?
Hi Ann, this is pretty soft cake, so it would be difficult to slice horizontally. Plus, the added batter in each pan may cause the cake to bake unevenly. It’s best to make four separate layers or, see recipe notes for three layer instructions.
Sorry if been asked before! Is it ok to create the whole cake as pictured (as in the mousse and ganache in/on it) and leave the cake ready to serve in the fridge overnight before serving it the next day?
Hi Justine, you can leave the cake in the refrigerator overnight without issue. The ganache will harden a bit in the fridge, but the cake can be served at room temperature or chilled. Hope it’s a hit!
Best chocolate cake ever!! This is the second cake recipe I used of yours in one week. The first was the strawberry cake , which was AMAZING, and now this chocolate cake. I was a little leary at first when I saw how thin the cake layers were (I used 9” cake rounds) but it turned into to a beautiful layer cake. The mousse filling was to die for and was the perfect amount. The chocolate ganache was a dream to work with and was so easy to smooth over the cake. I wish I could submit a picture to show you how beautiful it was!
★★★★★
Was wondering about the chocolate chips! It doesn’t say to melt them before folding them in, so I assume I just plop em in as-is?
Hi Nolan! Yes, the chocolate chips are an optional mix-in to the batter.
This recipe is off the charts awesome and made it for my husband’s birthday! I am making it now for my son’s birthday but want to frost with buttercream frosting. Is that ok? Should I do the crumb layer with buttercream and not mousse?
Hi Meg, yes, you can use buttercream here instead. We still recommend a crumb coat — with buttercream will work just fine!
Hi, can I use self raising flour instead of all purpose flour is i leave out the baking powder/baking soda?
Hi Emma, we don’t recommend it. Self-raising flour isn’t always a 1:1 swap with the all-purpose flour + rising agents, so it would take some recipe testing to determine the proper swap. Best to stick with all purpose flour here.
I make this cake for my brother’s birthday every year because he loves it so much! The only thing is, we don’t like the chocolate ganache on top. It’s too thick and takes away from the fluffyness of the mousse and cake. Instead I double the mousse and it comes out amazing.
★★★★
Could I use some type of coffee to make the chocolate mousse a mocha mousse? Thank you!
Hi Sara! We haven’t tested a mocha mousse recipe. You start with adding extra espresso powder – let us know if you give it a try!
Can I bake this as a sheet cake? It would be much easier for me.
Hi Mary, You can bake this cake in a 9×13 inch baking pan. Same oven temperature, about 35-40 minutes bake time.
Regarding the conversion to Cupcakes. Do I have the actually HALVE the QUANTITIES in both recipes you suggested then mix them together to make the Mousse Cupcakes ???
Hi Dale, you can make cupcakes using this cake batter rather than the chocolate cupcakes, and use the full amounts of mousse and ganache. You simply will have a larger yield of cupcakes.
Hi Sally. The chocolate mousse looks divine. Can the mousse be used as a frosting on its own for another cake I’m baking? Will it hold its shape if the cake is cold?
Hi Panjami, You can use the mousse to fill and frost a cake, just like we do here before the ganache is added. You won’t be able to pipe it but it should be fine to cover a chilled cake.
Hi Sally,
I really liked your very simple Ganache and Mousse recipe. I made the mousse but while mixing the cocoa + chocolate and whipped cream, I deflated the cream. Is there any way to salvage it? Can I whip it again after refrigerating for a couple of hours??
Thank you
★★★★★
Hi Bhavi! The most common cause of a thin mousse is over mixing. If you try it again, avoid over-mixing which can deflate/thin out the mousse. And also, make sure you chill it in the refrigerator for at least 2 hours before using. Unfortunately, there’s no great way to re-whip it once combined.
Thank you Sally. I think I mixed the chocolate mixture with the whipped cream while it was still warm. Anyway I’ll try to see how it turns out. I need the cake tonight so may not be able to wait for another batch after 2 hours! Hoping for the best! Thank you for the reply!
Hi! Could I halve the recipe and use 4 4-inch cake pans?
Hi Elsie, that should work — be sure to only fill your pans half way and use any leftover batter for a few cupcakes. We’re unsure of the exact bake time. This cake pan sizes and conversions guide may be helpful in the future, too!
By far the best homemade chocolate cake I’ve ever made. I made this for my Mom’s birthday this weekend and it was a huge hit. Moist, deep chocolate flavor throughout and the mousse and ganache – perfection! I will definitely make this again.
★★★★★
By far the best homemade chocolate cake I’ve ever made. I made this for my Mom’s birthday this weekend and it was a huge hit. Moist, deep chocolate flavor throughout and the mouse and ganache – perfection! I will definitely make this again.
★★★★★
I first made this cake back in July for my wife’s birthday. She loved it so much, she immediately recommended it for a friend’s upcoming birthday celebration. As I prepare to make this cake for a second time, I wanted to reach out with a word of thanks. This cake recipe is absolutely delightful, a fun and manageable project delivers exactly as promised. It haunts, it makes you ruminate and drives to distraction. So much fun, Cheers!
★★★★★
Wow,was this delicious! The many steps were worth it. My taste testers felt that the cake needed a deeper chocolate flavor with more moist texture,but overall a very luxurious taste.
★★★★★
I’ve done this recipe before but with cupcakes but I cant remember how long to cook them for. I thought I saw it in the comments. it said how full to fill them and how long.
Hi Nicole, you sure can make these as cupcakes! See section titled “What about cupcakes?” for more details.
Can this cake be made in a 13 x9 x 2 glass pan and is it enough to make 2 at this size?
Hi Sally! I only have 1 cake tin at home.. do you think I could pour all the batter into the 1 tin and split it in half after it cools, or is this going to end up a crumbled disaster? Thank you!
Hi Emily, we don’t recommend baking it all in one cake pan, as it could overflow and bake unevenly. Rather, you can bake the layers one at a time, leaving the leftover batter covered with a clean towel at room temperature while waiting for the current layer to bake. Hope you enjoy the cake!
Will this cake stand up to fondant coating?
Shouldn’t be a problem!
Hi Sally, my nephew asked me to make a chocolate mousse cake for his birthday, of course I said yes. I have never made a chocolate mousse cake before. Then I came across your Dark chocolate mousse cake recipe and it was absolutely delicious! I took a piece to make friend to taste and she asked if I could make it for her next birthday.