Easy chocolate mousse cake recipe makes a moist dark chocolate cake that’s topped with a simple, easy chocolate mousse. Easy homemade cake recipe that always gets rave reviews!
I like chocolate mousse anything – Chocolate Mousse, French Silk Brownies, and chocolate mousse brownies are just a few of the chocolate mousse treats that I love! So it isn’t surprising that this chocolate mousse cake is one of my favorite cake recipes!
This cake is moist and intensely chocolaty. It’s topped with a super rich and creamy chocolate mousse for the ultimate chocolate dessert.
And all of that chocolate in one little piece of cake means a super delicious dessert that’s perfect for birthdays, holidays, or any time you want something a little extra!
How to make chocolate mousse cake
In a medium bowl, whisk together flour, sugar, cocoa powder, baking soda, baking powder, and salt. Set aside.
In a large bowl, whisk together buttermilk and vegetable oil. Whisk in eggs one at a time.
Stir in dry ingredients until just combined.
Add hot water and vanilla. Whisk until just combined.
Pour batter into prepared baking dish.
Bake until wooden toothpick inserted in the center comes out clean. Cool to room temperature.
To make the chocolate mousse, add mini marshmallows, chocolate, and milk to a large, heavy saucepan.
Cook over low heat, stirring constantly, until melted and well-combined. Remove from heat, and cool completely.
In a large bowl, beat whipping cream and vanilla together to soft peak stage. Fold whipped cream into cooled chocolate mixture.
Spread over cooled cake. Chill for at least 30 minutes, or until ready to serve.
Tips
- Cocoa powder: I use regular unsweetened cocoa powder in this recipe. I’ve also used Hershey’s special dark cocoa powder. However, I haven’t tried Dutch-processed cocoa powder with this cake.
- Salt: If you don’t have kosher salt, use 1/2 teaspoon table salt instead.
- Buttermilk: Regular or low-fat will work. If you don’t have buttermilk, you can make a quick substitute with this recipe.
- Water: I use hot tap water about (150F).
- Semisweet baking chocolate: If you’d like a sweeter mousse, you can use milk baking chocolate.
- Milk: Any milk from skim to whole milk will work.
Tips for making whipped cream
If you haven’t made whipped cream (or would just like some tips), I have lots of tips and more pictures here.
Storage
The cake can be stored, covered, in the fridge for up to 5 days.
More chocolate cake recipes!
More chocolate cake recipes!If you’ve tried this chocolate mousse cake recipe, don’t forget to rate the recipe and leave me a comment below. I love to hear from people who’ve made my recipes!
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Chocolate Mousse Cake
Equipment
- 9x13-inch metal baking pan
Ingredients
Chocolate Cake
- 1 ¾ cups all-purpose flour
- 1 ¾ cups granulated sugar
- 3/4 cups unsweetened cocoa powder
- 2 teaspoons baking soda
- 1 teaspoon baking powder
- 1 teaspoon kosher salt
- 1 cup buttermilk
- 1/2 cup vegetable oil
- 2 large eggs
- 2 teaspoons vanilla extract
- 1 cup hot water not boiling
Chocolate Mousse
- 1 ½ cups mini marshmallows
- 8 ounces semisweet baking chocolate chopped
- 1/2 cup milk
- 2 cups cold heavy whipping cream
- 1/2 teaspoon vanilla extract
Instructions
Chocolate Cake
- Preheat oven to 350 F. Grease a 9x13-inch baking pan. Set aside.
- In a medium bowl, whisk together flour, sugar, cocoa powder, baking soda, baking powder, and salt. Set aside.
- In a large bowl, whisk together buttermilk and vegetable oil.
- Whisk in eggs one at a time.
- Stir in dry ingredients until just combined.
- Add hot water and vanilla.
- Whisk until just combined.
- Pour batter into prepared baking dish.
- Bake 30-40 minutes, or until wooden toothpick inserted in the center comes out clean.
- Cool to room temperature.
Chocolate Mousse
- To make the chocolate mousse, add mini marshmallows, chocolate, and milk to a large, heavy saucepan.
- Cook over low heat, stirring constantly, until melted and well-combined.
- Remove from heat, and cool completely.
- In a large bowl, beat whipping cream and vanilla together to soft peak stage.
- Fold whipped cream into cooled chocolate mixture.
- Spread over cooled cake.
- Chill for at least 30 minutes, or until ready to serve.
- Refrigerate any leftovers.
Video
Notes
- Cocoa powder: I use regular unsweetened cocoa powder in this recipe. I've also used Hershey's special dark cocoa powder. However, I haven't tried Dutch-processed cocoa powder with this cake.
- Salt: If you don't have kosher salt, use 1/2 teaspoon table salt instead.
- Buttermilk: Regular or low-fat will work. If you don't have buttermilk, you can make a quick substitute with this recipe.
- Water: I use hot tap water about (150F).
- Semisweet baking chocolate: If you'd like a sweeter mousse, you can use milk baking chocolate.
- Milk: Any milk from skim to whole milk will work.
- Nutrition facts are estimates.
Nutrition
Did You Make This Recipe?
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Originally published 10/14/16. Updated with additional photos and tips 2/5/21.
Cake portion adapted from Food Network.
Reader Interactions
Love this recipe?
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Comments & Reviews
Alison says
Delicious
Kate says
Thank you!
Renate says
This is a great recipe. I just made the following changes:
*Instead of oil, I used unsweetened applesauce
*I only used 1/2 cup sugar, since I knew the frosting would be sweet
*Instead of water, I used brewed coffee
*Milk, I used unsweetened Almond milk
My cake turned out pretty good. I will be making it again.
Thanks for sharing the recipe.
You can find me on Instagram @ blueozeannestdezignz
Kate says
Thank you so much for sharing your notes! It’s great to hear what has worked for other people!
Tracy says
I have made the chocolate mousse a few months ago and it was fantastic! I haven’t made the cake yet but definitely intend to. I was wondering if I could substitute white chocolate for the semisweet chocolate for the mousse next time I make it?Thank you for the wonderful
recipe!
Kate says
Thank you so much! I’ve tried making the mousse with different types of chocolate, like milk, semisweet, and bittersweet, and it has worked well with those types of chocolate. I would guess that white chocolate would work, but I haven’t tried it to say for certain. If you try it, I’d love to hear how it works out!
Vicki says
The most delicious moist cake and mousse topping ever! It was enjoyed by everyone celebrating our twin granddaughters birthday. I won’t hesitate to make it again. Thank for the recipe!
Kate says
Thank you so much!
Kristy says
I have a question. I was going to make this for my daughter’s birthday, but she categorically doesn’t like marshmallows. Can you taste the marshmallows in the mousse?
Kate says
I can’t taste the marshmallows, and I haven’t gotten any comments from anyone who has noticed the taste of the marshmallows. The mousse just tastes like chocolate to me!
Diane says
Very decadent and full of rich chocolate flavor! absolutely amazing! I cut it down to fit a square serving platter and frosted all sides. I’m planning to serve it with sliced strawberries
to lighten the richness of the chocolate.
Kate says
Thank you! Fresh raspberries are also good with this cake.
Sue says
Can’t wait to make this. Do you think this cake could be baked as double 8″ rounds?
Kate says
I haven’t tried that, but I think the cake should work well in 8″ rounds. The mousse filling is pretty soft, so you may need to chill it once you’ve frosted the first layer before adding the second layer. Hope that helps!
Shanna Garth says
This cake was a huge hit with my family! It was delicious even after refrigerating the small amount of leftovers. I am definitely making this again. Thank you!
Kate says
Thank you! I’m glad it was a hit!
Blimey says
This looks sooo good, would love to try it.
I do have a question though.
I see it calls for mini
Marshmallows, can that be substituted with Marshmallow Fluff?
(B/c of an Allergy? ) & if so… how much would you say? (I’m also guessing… & can be wrong… that it doesn’t need to be cooked then.??
Thanking you in advance
Kate says
Hi! I’m not sure how marshmallow fluff would work in this recipe. Marshmallow fluff doesn’t have gelatin, so it may not add the same volume to the mousse. You could also try chocolate whipped cream in place of the mousse as a topping for the cake.
Patty says
I made this recipe today. It was GREAT!! The cake was very moist and had a perfect amount of chocolate flavor. The mousse has a wonderful consistency and very light. I would highly recommend anyone considering making this to definitely do it. You’ll be happy you did!! I’m so happy I found it!!
Thank you!!!
Kate says
Thank you so much!
Sue says
This was so amazingly delicious! Made it for my sons birthday. He said that it was the best chocolate cake he’s had in years!
Kate says
Thank you so much!
Karen Stewart says
My husband was recently diagnosed with mild diabetes so we are watching carbs and sugars but this cake looks so amazing we will have to try it sometime.
Do you know if stevia could be used instead of or perhaps part of the sugar in the cake as well as in that yummy looking mousse frosting?
Thanks very much,
Karen Stewart
Kate says
Hi! I wish I had a more definitive answer for you, but I haven’t tried stevia in the cake. I would guess that a chocolate like Lily’s that is sweetened with Stevia could be used to make the mousse, but I haven’t tried that either to say for certain.
Billie says
A 1:1 sugar substitute like erythritol/monkfruit blend might work better in the cake. It might affect the texture a little bit but it should be pretty good. You might have to make a more traditional mousse for the top to remain completely sugar free. There are max mallows made with erythritol but I have no idea is they would work in this.
Alicia says
This cake is amazing! I made this for my son’s birthday and it was a hit. It is now one of our new family favorites. Perfectly moist and not too sweet. I don’t usually eat desserts but I loved this.
Kate says
Thank you so much! I’m so glad that it was a hit!
Barbara says
Can you use chocolate chips for the baking chocolate?
Kate says
I haven’t tried that in this recipe to say for certain.
Peggy says
This cake was so delicious. The cake was very moist and the mousse frosting was light and fluffy. My family loved it. I will definitely be making this cake again. Thank you for sharing this fabulous recipe.
Kate says
Thank you so much!