Dark Chocolate Mousse Cake

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.

dark chocolate mousse cake

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.

chocolate layer cake

3 Parts to Dark Chocolate Mousse Cake

Let’s break down each component of this intensely rich cake:

  1. 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.
  2. 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.
  3. 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!

4 layer chocolate cake

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!!

chocolate cake batter

Simplified Chocolate Mousse

The chocolate mousse adds a creamy and light contrast to the dark chocolate layers. You need 6 ingredients:

  1. Hot Water
  2. Cocoa Powdernatural or dutch-process
  3. Melted Chocolateuse two 4-ounce chocolate baking bars found in the baking aisle
  4. Heavy Cream
  5. Confectioners’ Sugar
  6. 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.

making chocolate mousse

Whipped cream + our chocolate mixture. ↑

Fold them together to make our chocolate mousse filling. ↓

chocolate mousse for chocolate cake

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 on chocolate cake

Chocolate Ganache

I won’t go into a lot of detail about the chocolate ganache because I have a complete chocolate ganache recipe 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. 🙂

top of chocolate mousse cake

chocolate mousse cake

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

Print
4 layer chocolate cake

Dark Chocolate Mousse Cake

  • Author: Sally
  • Prep Time: 2 hours, 30 minutes
  • Cook Time: 25 minutes
  • Total Time: 5 hours, 55 minutes
  • Yield: serves 10-12
  • 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 (220g) all-purpose flour (spoon & leveled)
  • 3/4 cup (65g) 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

  1. Preheat oven to 350°F (177°C). Grease four 8-inch or 9-inch cake pans, line with parchment paper, then grease the parchment paper. Parchment paper helps the cakes seamlessly release from the pans.
  2. 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.
  3. 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.
  4. Remove the cakes from the oven and set on a wire rack. Allow to cool completely in the pan.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. Cover leftover cake tightly and store in the refrigerator for 5 days.

Notes

  1. 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.
  2. 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 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.
  3. 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.
  4. 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.)
  5. Why Room Temperature? All refrigerated items should be at room temperature so the batter mixes together easily and evenly. Read here for more information. Instead of sour cream, you can use plain yogurt. The cake won’t taste as rich, but it’s a fine substitute. If needed, you can use whole milk mixed with 1/2 teaspoon of white vinegar or fresh lemon juice instead of buttermilk.
  6. 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

 

171 Comments

  1. I love your cake stand you used! I have been wanting one for a while now. Do you mind telling me where you got it? BTW your cake is gorgeous and I will totally be trying it soon since my whole family is chocolate crazy!

    1. Thank you so much! This one is from Pier 1 a few years ago (I believe!), but I know World Market usually carries them too. Give a search online!

  2. Hi Sally – this looks like the perfect cake for me to bake for my daughter’s birthday this weekend! Do you assemble it on a cake board, then transfer it to the stand?

      1. Thanks, Sally! I made the cake yesterday, and it was a huge hit at the birthday party! I made a few changes to the recipe to make the chocolate flavor less intense, because of personal preference. One of the best cakes I’ve ever made!

  3. Made this today for a birthday and it turned out really great! Moist, chocolatey and delicious. It was certainly rich, but that didn’t stop us from going back for seconds! Thanks for another great recipe Sally – this one is a keeper!

    1. Hey sally! Love love all of ur recipes but the only problem this time is that we dont use sour cream in our recipes so it is difficult to find one What can i use as a sub for sour cream?

      Regards

  4. Hi Sally,
    I was wondering where you got your cake stand? I have been wanting a wooden one for a while and yours is very beautiful! I will totally be making this cake soon!(Especially since it is chocolate! My whole family is chocolate crazy!)
    -Zoe

    1. Hi Zoe! This one is from Pier 1 a few years ago (I believe!), but I know World Market usually carries them too. Give a search online!

  5. Very good cake! So simple and delicious! Will make again for my mom’s birthday since she loves that dark, rich chocolate taste!

  6. Hi Sally, love your recipes. My husband would love this cake! Would it matter if I used olive oil instead of vegetable or canola oil?

    1. Hey Sally! I’m new to baking and always wanted to learn how to bake and I came across your blog. All your recipes look delicious and couldn’t choose which I should try first until I saw this one. I wanted to surprise my bf for his birthday and make this cake and he LOVES chocolate. I’ve never used buttermilk. In my store theres a dry buttermilk and I was wondering do I just mix that by following the steps or add that as dry ingredients? Or do I mix the dry buttermilk and water?

      1. Hi Angel, You can use the powdered buttermilk and mix it with water as instructed on the container. You will need 1/2 cup of liquid buttermilk as stated in the recipe. I hope you both love the cake and that he has a great birthday!

  7. I made this in 3, 8” layers and followed Sally’s time recommendation and it was perfect.

    With this cake and Sally’s triple chocolate, I replace about 1/3 of the cocoa with KAF’s Black Cocoa and I am a fan of the results. The mousse is excellent.

    1. I’m thrilled you enjoyed this recipe, Melanie! Thank you for your positive feedback- and what a great tip! I’ll look into the KAF black cocoa 🙂

  8. Made this using the combination of Special Dark cocoa and regular cocoa that Sally recommends and it turned out perfect! Filled it and covered it with peanut butter frosting and then did a dark chocolate ganache drip. It was awesome!!

    1. Sounds absolutely incredible, Kelly!! Can’t go wrong with chocolate + peanut butter 🙂 Thanks for your positive feedback!

  9. I am making this cake with the information and the products needed and will be making this (hopefully done right) and will make it close to 3 of my friends party on 8/25/19. I am honored to make it.

  10. Hi Sally! Looking forward to making this cake for family this weekend. I have King Arthur flour double Dutch dark cocoa in my arsenal. Can I use that in place of Hershey special dark cocoa powder? Thanks. As always. Your the best!!!

    1. Hi Rosemarie, You can use the King Arthur dutch cocoa instead of the Hershey’s special dark. 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.

  11. This cake was delicious! I used bittersweet chocolate for the mousse, but semisweet for the ganache. It came out perfectly. Intense chocolate flavor and definitely not too sweet. It was definitely a crowd pleaser!

  12. I am worried that the ganache will turn hard once it is refrigerated and will be difficult to cut clean slices and that the ganache will crack and crumble.

  13. Hi Sally! I made 2 of your cake recipes for a joint birthday party and they were delicious! Thank you! I am making this one for my other daughter’s birthday party in 2 weeks. I did read about freezing recommendations but I just want to make sure I get it right. You don’t recommend freezing the whole cake with the mouse and ganache, correct? I froze the other ones but they didn’t have mousse and ganache. It helps me a lot to freeze ahead of time because I do all the food for our parties. Thank you!

    1. Hi Jill, The frosted cake freezes well also, up to 3 months! Thaw overnight in the refrigerator, then bring to room temperature or serve cold. Enjoy!

    1. Hi Amu! I recommend halving the mousse. Having the ganache should be enough too but you can try 6 ounces chocolate and 3/4 cup heavy cream just to be sure there’s enough!

  14. The mousse turned out far too thin to be spread on the cake! Admittedly, I refrigerated it for the minimum 2 hours. How can I thicken it?!

    PLEASE HELP!!

    1. Hi Michael, When you whipped cream, sugar, and vanilla together did you get it to reach medium peaks? Then when you combine this whipped mixture with the chocolate be careful to very gently fold them together. Over-mixing at this step will deflate/thin out the mousse.

  15. I made 1/2 of this recipe for my husband’s birthday cake. Baked in a 8*8 pan, cut in half and stacked layers. On the bottom before I baked I had made a pecan praline mix. Then frosted with sweetened whipped cream. It was amazing. Another great recipe Sally. Thanks!

  16. Such a beautiful and delicious cake! Super chocolatey and not too sweet, the best! Leftovers were eaten for breakfast standing in front of fridge. With a fork because I’m ladylike.

  17. Such a rich, decadent, moist cake! The combination of dark chocolate and coffee is amazing! I added espresso powder to the ganache and used espresso morsels in the cake batter to give it an added depth of flavors. I also made it in three layers. Love, love, love this recipe!

  18. I made this last weekend over the course of two days. The cake was delicious and very rich, I loved the deep chocolate flavor! Your recipes never disappoint!

  19. Hi Sally!

    Can’t wait to try this recipe, yours are always a massive hit!

    Please can you suggest an alternative to buttermilk please as I can’t find it where am I 🙁

    Thank you so much,
    Grace

  20. Absolutely the most tasty and moist chocolate cake I have ever made. I have been baking your recipes for a long time and they never fail. Thanks.

  21. Oh my my! This chocolate cake is so delicious. My first attempt isn’t so pretty but it tastes amazing. I tried pre-making the ganache but it was too hard to spread over after being refrigerated & never quite soft enough again after sitting out for awhile so I quickly & easily made another batch to pour over. Thanks to another review I found out about using powdered buttermilk which is so handy for baking.

    1. Hi Kat, This cake already has cocoa powder— which is a VERY fine dry ingredient. The combination of cake flour and cocoa powder usually results in a flimsy cake.
      I have so many other cakes that call for cake flour, I’m sure you will find a way to use up your box! Here they all are: https://sallysbakingaddiction.com/tag/cake-flour/

  22. Hi sally! I’m making an assortment of 3-4 different types of cupcakes for my sisters birthday party and I’m trying to figure out which of your recipes to decide on..they all are incredible! But I LOVE this cake and I was wondering if the chocolate moose could be used to create a pipped frosting on top of the chocolate cupcakes? Thanks!!

    1. Hi Lindsey, For cupcakes I usually fill the cupcakes with the mousse and then top them with a bit of the ganache. However, you can certainly just go ahead and pipe the mousse on top! It’s not sturdy enough for intricate piping but will still taste delicious!

  23. What an amazing cake! I made this for my husband’s birthday and it was huge hit. The cake is moist and mega-chocolatey and the mousse is beautifully light. I will definitely be holding on to this recipe!

  24. Love this recipe, it is going in my family cookbook for sure. It is SO chocolatey and not excessively sweet. Each element is excellent- the cake is moist with deep flavour, the mousse is fluffy and rich and the ganache is a lovely finish. I will absolutely make this again.

  25. What a great recipe! A friend of mine asked me to bake a cake for her girls’ birthday party (she hates baking) and I tried this one out for the first time for the occasion (always a risk). I decorated it with dripping chocolate ganache and went over the top with decorations of chocolate waffles, melocakes, maltesers and chocolate sticks. It looked spectacular (if I say so myself) but it tasted just as good too! All the kids loved it and I scored big time My kids have requested the exact same cake for their upcoming birthday parties! So thank you so much for sharing this recipe!

  26. Hi Sally,
    I made this cake for my daughter’s 25th birthday party. She loves chocolate so this cake was perfect. It was delicious, moist and not too sweet. I decorated it with white chocolate curls, raspberries and edible gold stars. It looked impressive and people asked where I bought the cake. Thank you for a super delicious recipe.

1 2 3

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

With kitchen-tested quality recipes and step-by-step tutorials, my goal is to give you the confidence to bake and cook from scratch.

Recipes You’ll Love

Archives

Categories

Sally's Baking Challenge

Join the community on the 1st of every month as we tackle a new challenge recipe.

View More

Sally's Cookie Palooza

A tradition since 2013, every December we countdown to Christmas with 10 new cookie recipes in a row!

View More

Sally's Pie Week

The first week of every November is all about Thanksgiving Pies.

View More

My Cookbooks

About Sally

Welcome to my Kitchen!

I’m Sally, a cookbook author, photographer, and blogger. My goal is to give you the confidence and knowledge to cook and bake from scratch while providing quality recipes and plenty of pictures. Grab a cookie, take a seat, and have fun exploring! more about Sally

×