Elegant, moist and delicious Chocolate Mousse Cake recipe filled with an easy homemade chocolate mousse, and warm chocolate frosting poured on top.
Want more cake recipes? Try my German Chocolate Cake, Berry Cake, or Coconut Cake with Pineapple Filling!
Why I love this easy mousse cake:
- Prep Ahead – The chocolate mousse recipe couldn’t be easier to make, and you can prep everything in advance!
- Elegant – Fancy enough to impress any guests, especially a chocolate lover!
- Delicious – The chocolate cake is moist and divine. The chocolate mousse filling is creamy and pairs perfectly with the cake. This will become your new favorite cake!
How to make Chocolate Mousse:
Make the Mousse: Start by mixing the cocoa powder and hot water together until smooth. Melt chocolate chips in the microwave, or using a double boiler. Add the cocoa powder mixture to the melted chocolate and stir until smooth. Allow to cool to room temperature.
Whip the cream and sugar together in a large mixing bowl until very stiff peaks. Add the cooled melted chocolate and gently fold the mixture together to combine. Refrigerate until ready to use.
How to make Chocolate Mousse Cake:
Bake Chocolate Cake: Stir together sugar, flour, cocoa powder, baking powder, baking soda, and salt in a large bowl. Add eggs, milk, oil, and vanilla. Beat on medium speed for 2 minutes. Stir in boiling water then pour into prepared pans. Bake at 350 degrees for 30-35 minutes, or until a toothpick inserted comes out clean. (If you don’t want to make the cake from scratch, you can use a box cake mix).
Halve the Cake Rounds: Once the cakes have cooled use a sharp serrated knife to torte them in half, lengthwise, so you have four thin layers of chocolate cake.
Stack Cake with Mousse Filling: Place the first cake layer on your serving tray. Smooth a thin layer of chocolate mousse over it, and top with the next layer of cake. Repeat to assemble a cake with chocolate mousse between each layer. Smooth any extra chocolate mousse you have over the outsides of the entire cake to make a”crumb” coat to seal the cake.
Refrigerate the cake for at least 30 minutes (or up to 1-2 days, covered) while you make the chocolate frosting.
Make Frosting: Combine milk, cocoa, and butter in a medium saucepan. Bring to a boil then remove from heat. Add powdered sugar and mix with electric beaters to get rid of any lumps. Cool for at least 15-20 minutes, stirring occasionally. Be sure to allow the frosting to cool long enough. You want it soft enough to still be “pourable” but you don’t want it to be so warm that it melts the mousse into a puddle.
Pro Tip: Lay pieces of parchment paper around, and gently under the edges of the cake to catch the frosting as it drips down. I usually just pour the frosting slowly and catch it as it comes down the sides of the cake, smoothing it along the sides of the cake.
Make Ahead Instructions:
- Chocolate Mousse: Place in an airtight container in the fridge for up to 5 days. Fold it again gently with a spatula before using. But the texture is best the day of.
- Cake Rounds: These can be made in advance and frozen. Once baked, cool them completely and then wrap them in a double layer of plastic wrap. Place in a freezer safe bag and freeze for up to 3 months.
More Desserts to Try:
- Chocolate Peanut Butter Cake
- Plum Cake
- Chocolate Milkshake
- S’mores Bars
- Panna Cotta
- Tres Leches Cake
- World’s Best Peanut Butter Bars
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Recipe
Chocolate Mousse Cake
Equipment
Ingredients
Chocolate Cake:
- 2 cups granulated sugar
- 1 3/4 cups + 2 Tbsp all-purpose flour
- 3/4 cup unsweetened cocoa powder
- 1 1/2 teaspoons baking powder
- 1 1/2 teaspoons baking soda
- 1 teaspoon salt
- 2 large eggs
- 1 cup buttermilk
- 1/2 cup oil (vegetable or canola oil)
- 2 teaspoons vanilla extract
- 1 cup boiling water , or hot coffee
Chocolate Mousse:
- 1/2 cup hot water
- 4 Tablespoons unsweetened cocoa powder
- 1 1/2 cups semi-sweet chocolate chips
- 2 cups heavy whipping cream
- 2 Tablespoons granulated sugar
Chocolate Frosting:
- 6 Tablespoons milk
- 3 Tablespoons unsweetened cocoa powder
- 1/2 cup butter (one stick)
- 3 3/4 cups powdered sugar
Instructions
Chocolate Cake:
- Heat oven to 350°F. Grease and flour two 8 or 9 inch round baking pans. (I like to line the bottom of mine with wax or parchment paper).
- Stir together sugar, flour, cocoa powder, baking powder, baking soda and salt in large bowl.
- Add eggs, buttermilk, oil and vanilla; beat on medium speed of mixer 2 minutes.
- Stir in boiling water (the batter will be thin). Pour batter into prepared pans.
- Bake for about 30 to 35 minutes or until a toothpick inserted in the center comes out clean.
- Allow cake to cool in the pan for 5 minutes and then remove to wire cooling racks. Cool completely. (You could freeze the cake rounds at this point, if desired.)
Chocolate Mousse:
- Stir the cocoa powder and hot water together. In a double-boiler (or in the microwave) melt the chocolate chips, just until smooth. Add the cocoa mixture to the melted chocolate chips and stir well to combine. Allow to cool to room temperature.
- In a separate large bowl, beat the cream and sugar until very stiff peaks form. Add the chocolate mixture and fold in with a spatula until well combined. Refrigerate until ready to use, up to 5 days.
Chocolate frosting:
- In a medium saucepan, add milk, cocoa, and butter. Bring to a boil. Remove from heat.
- Add powdered sugar and mix with electric beaters to get rid of any lumps. Allow to cool for 15-20 minutes, stirring occasionally.
Assembly:
- Once cakes have cooled, use a sharp serrated knife to torte each cake (cut each cake evenly in half, horizontally, so that you end up with four, thin, 9” cake pieces).
- Place your first cake layer on your cake serving plate. Spread a big spoonful of mousse on top of that cake layer. Repeat with the remaining cake layers, adding a layer of mousse filling between each layer of cake.
- Use remaining mousse filling to spread it evenly around the entire outside and top of the cake. Refrigerate for 30 minutes.
- (I usually make the warm chocolate frosting while the cake is in the fridge.)
- Remove cake from fridge and very slowly pour the cooled chocolate frosting over the top. Use a spatula or knife to gently spread the frosting evenly over the outside of the cake as you pour.
- Refrigerate until ready to serve.
Notes
- Mousse: Place in an airtight container in the fridge for up to 5 days. Fold it again gently with a spatula before using. But the texture is best the day of.
- Cake Rounds: These can be made in advance and frozen. Once baked, cool them completely and then wrap them in a double layer of plastic wrap. Place in a freezer safe bag and freeze for up to 3 months.
Nutrition
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*I first shared this recipe in May 2014. Updated May 2018 and February 2022.
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That cake looks so yummy! I would like to try your recipe.
If I’m making this the night before, serving the next day, would it be okay to make it all including the warm frosting on top then store in the refrigerator for the night?
Hi Lauren, I would suggest adding the frosting, letting it cool, and then flash freezing the cake (stick it in the freezer for about 15 min.) before covering it. Then cover it well with plastic wrap and tinfoil. I would suggest sticking it back in the freezer overnight (Ive never tried it in the fridge but I’m sure it would be fine too…)
I think I will give this a try this weekend. One question though, do I let the chocolate part of the mousse cool before adding the whipped cream? I would be afraid it may break it down.
I live to bake and at church the youth are always thrilled when I sign up to bake for a gathering. Thanks for sharing such great ideas!
Hi Jill, you definitely don’t want the chocolate part to be hot–wait til it’s just warm or close to room temperature but not hardened.
This is good to know about the mousse as some new bakers may not know to let it cool. Suggestion to add to the recipe instructions to let the mousse cool before adding to the whip cream 🙂 I’m sooo looking forward to this mousse. My chocolate is cooling now! Thanks so much! 🙂
I totally didn’t let it cool!! 🙁 Now it seems really soupy…will it thicken up after cooling in the fridge? Thank you! Tastes really good, though lol 🙂
The same thing happened to me. 🙁 I don’t know what to do. The recipe does not tell you to let it cool first. For us bakers who follow recipes to a T – you should probably add. I’m going to pray it hardens a bit in the fridge.
Hi Danielle, I apologize–I’ve updated that in the recipe!
I made this today, its sooooooooo delicious! I’ll definitely make again! Thank you!
Thanks Christy, soo glad you liked it!
Hi! Making this right now… After the cake has cooled, it is very sticky. Should I have used wax
or parchment to help take it out of the pan? Some of it stuck to the bottom even after I generously buttered and floured. It also stuck to my hands as I tried working it out of the pan… What am I doing wrong? Thanks! 🙂
Hi Andrea, what type of pan are you using? If it’s not a nonstick pan I would definitely put wax paper on the bottom, and then also spray well with cooking spray…
Hi! I used 2 non-stick 9″ rounds. I am making it again today, I will use parchment for sure. This is the best chocolate cake I’ve ever made….and it lasted perfectly in the fridge for a week, covered in wax paper. DELISH!!
So happy you liked it! Thanks Andrea!
The cake is delish! But the frosting was too thick. I added another half stick of butter and more milk. I think you may have made an error in one of the ingredients above. Maybe the milk?? I don’t know, but either way, it is very good.
Thanks so much, I love to hear that you liked it! I did adjust the frosting ingredients so it should be perfect now! Thanks for your comment 🙂
Awesome recipe! 🙂 I made this today ~ followed the instructions carefully – the frosting didn’t pour out but I was able to spread it on the cake & it tasted great. I followed the ingredients & instructions carefully — any tips (cut back on powdered sugar? maybe do 3C instead of 3 3/4C?) it looks delicious though – can’t wait to try a piece!! 🙂
Hi Tina, thanks for your comment and input! Glad you liked it!
I Can’t wait to try another recipe off your blog …. I love to bake. I thank my grandma for endless days of sitting on her huge island as a child while she baked almost daily … such a great creative outlet and the outcome is always (well, usually) De-Lish! lol 🙂
I just made this tonight it’s amazing, however my frosting did not pour out? It was still good just didn’t look pretty because it didn’t pour. I can’t figure out what I did wrong. Any suggestions I followed the recipe.
I’m glad you liked it! As far as the frosting–it’s always been pourable for me, so that’s weird… Next time I would try adding a little less powdered sugar, and don’t wait for it to cool 5min–just pour it right over!
WOW! This looks so amazing! Talk about chocolate heaven. Thanks for sharing!
Lauren, this is AMAZING. It looks like the infamous chocolate cake from Matilda where poor Ralphie has to consume!
Hahahaha it totally does! And, it was made with my “sweat and tears”! 😉 I think normal people would have been grossed out by that scene but it always made me crave chocolate cake! haha
I’m the same way! It was disgusting but I always craved chocolate cake once the scene was over!
Oh my goodness, this is making my mouth water! Looks so moist and flavorful! Pinning!
It’s seriously amazing!! Hope you get a chance to make it!
Hi! I ‘d just like to find out whether it would be possible to make the chocolate frosting before hand and then reheat it (perhaps over a double boiler) once I decide to ice the cake?
Hi there, that should be fine–refrigerate it until ready to frost them cake. You could heat it on low power slowly in the microwave or on the stove–add a tiny bit of extra milk if you need to, but once it’s barely smooth and stir-able you should be able to frost the cake easily. Good luck!
Thank you, that’s a huge help!! 🙂