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
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Comments & Reviews
Lynne says
Made this in two 8 inch round pans, then split the layers into 4 layers. Brushed the layers with simple orange sauce. Used the mousse between the 4 layers, then frosted it with a chocolate frosting. Perfect, delicious anniversary cake. Thanks
Kate says
How fun! That sounds like a delicious twist on the cake. Thanks for commenting!
Linda says
Would the buttermilk and eggs have to be room temp before mixing everything? I’m just curious because I’m afraid the hot water (not boiling) would somehow curdle/ cook the eggs/ buttermilk.
Kate says
I haven’t had that happen. As long as you whisk the eggs in well when you add them, there shouldn’t be any issues.
Genny Cox says
This was a very delicious cake! I added a ganache on the top made with dove dark chocolate and heavy whipping cream.
Kate says
Thank you! The ganache topping sounds delicious. =)
Veronica Mares says
Made this cake on Friday for my sons birthday and it was moist and delicious. Followed recipe directions except instead of the semisweet baking bars I used milk chocolate. That’s my family’s preference. Will make again.
Kate says
That’s fantastic! So glad that you and your family enjoyed the cake.
Jenn says
Hi, thanks for this recipe. It turned out amazingly moist and delicious! Just wondering if I need to store it in the fridge or can it be put into an airtight container?
Kate says
Hi! Glad that you liked the cake! I store it in the fridge.
Jennifer Bruns says
Recommendation for cooking temp/time and measurements for high altitudes.
Kate says
Hi! I don’t have a way to test high altitude adjustments, so I’m afraid that I can’t test any of the recommendations first.
Louise says
My frosting was bitter and thee cake tasted good enough but on the dry side. I followed to a T. The mini marshmallows did measure tight or loose?i did in between tightly packed and loosely packed. I was sad and disappointed with the outcome. Please advise what I possibly did wrong.
Kate says
I haven’t had anyone report the issues that you’re describing, so it definitely sounds like some things went wrong!
First, did you use unsweeteend chocolate instead of semisweet chocolate? That would give you bitter mousse. Between the semisweet chocolate and the marshmallows the chocolate mousse shouldn’t be bitter. If you like things on the sweeter side, though, you can use an equal amount of milk baking chocolate in place of the semisweet chocolate for an even sweeter chocolate mousse.
I’m surprised that your cake was dry because this is a super moist cake. Without knowing more, I would guess that the cake overbaked. If you used a dark metal pan or a glass pan and didn’t adjust for those or if your oven bakes hot, that could easily cause the cake to overbake and lose moisture. I hope that helps!
Genny Cox says
To make cakes more moist, make them a day ahead of time, let them cool and then wrap them and freeze over night. Then let them thaw naturally. It will help with frosting them too!
María Elena Orellana Fernández says
Hola Kate!!, Primero quiero felicitarte por tu página tan bonita. Me gustan mucho tus recetas porque además de deliciosas tus explicaciones son muy bien desarrolladas. Hoy preparé este chocolate mousse y me resultó perfecto. Muchas felicidades y gracias por las recetas, saludos……María Elena
Kate says
Hello! Unfortunately, my Spanish is a little rusty, so I have to respond in English. =) Thank you so much for your kind words! I’m so glad that the cake turned out well for you! Thanks so much for commenting.
Debbie says
I was craving some kind of mousse and found this recipe. Love the cake, LOVE, LOVE, LOVE the mousse topping. I will give you credit for the extra pound I picked up. ;)
Kate says
I’ll take that credit! ;) I’m glad that you liked the cake! Thanks for commenting.
Jo says
One of the best cake and frosting recipes ever! I’ve made it in a 9″x13″, two 9″ rounds and cupcakes – all came out delicious. Thank you for sharing!
Kate says
Thank you! And thank you for your note about making it in cupcake tins! It’s helpful to hear that that worked out well. Thanks for commenting! =)
Jo says
I’ve shared this pin with so many people after they ask for the recipe!!! And it’s my husband’s and youngest daughter’s #1 request four the weekends!
Kate says
Thank you so much!!
Melissa says
Have you ever used this recipe for cupcakes? If you think it would work, what would the bake time be?
Kate says
I haven’t tried to make this cake as cupcakes. The usual bake time for cupcakes is 18-25 minutes, but I’m not sure what it will be with this one. If you try it, I’d love to hear how it turns out!
Rita says
What is1/2 c what measurement is this
Kate says
1/2 c is 1/2 cup. Hope that helps!
Donna Queen says
Can regular milk be used Instead of buttermilk???
I’m not a fan of buttermilk
Kate says
The acid in the buttermilk helps to activate the baking soda, so it’s best to use buttermilk.
Elizabeth Ann Olson says
Absolutely the best chocolate cake I’ve ever made or eaten! Like in a previous comment, I used 1 cup of hot coffee instead of hot water. The recipe is easy to follow. My guests just loved it! I made it for my daughter’s birthday, so made it in two 8″ round layers. The mousse frosting was plenty for the filling and frosting all over, and there was enough to decorate the top with some edging and large star-tip swirls. Thanks so much!
Kate says
I’m so glad that you liked it! That’s a huge compliment! =D Also, thank you for your notes about making it in layers; that’s very helpful. Thanks for taking the time to come back and comment!
Brent Adams says
Can this be frozen after frosting with the mousse without affecting consistency or quality?
Kate says
Hi! I haven’t tried freezing the mousse. If I were going to freeze it, I would freeze the cake unfrosted and then make the mousse when you’re ready to serve it.
Gerianne says
Awesome, easy recipe! DELICIOUS!! :)
Kate says
Thank you so much! I’m so glad that you liked it. =) Thanks for commenting!
Mindy says
I love to bake chocolate cake and make a different recipe each time. This was one of the best I’ve made so far!! I used dark chocolate cocoa and hot coffee for the hot water and it was delicious. My whole family devoured it. The mousse turned out perfect and was a nice change from sweet buttercream frosting .
Kate says
I’m so glad! Thank you for your note about using hot coffee. I’ve had people ask about using coffee, but I hadn’t tried it. Thank you for taking the time to comment! =)
Sally says
That s was maybe the best choc cake I ever made! Will absolutely keep this recipe. The batter was quite thin, so I did not add all the water. I omitted about 1/3 c of the water.
Kate says
Thank you! I’m so glad that you liked the cake! And thank you for coming back to comment! =)
Alina says
Would substituting the vegetable oil with canola or olive oil work?
Kate says
It will! For the olive oil, you may find that you have some of the olive oil flavor in the background unless you use a light olive oil. Otherwise, either canola or olive oil will work. Hope that helps! =)
Becky Nguyen says
I made this for my husband for our anniversary and it was so incredible that he’s requested again for his birthday! Both the cake and the mousse are so delicious. It keeps very well for several days.
Kate says
Happy anniversary! That’s high praise when someone requests a cake for their birthday. =) I’m glad that you two enjoyed the cake! Thanks for coming back to comment.
Silvia says
I made this cake today and let me just say, it was absolutely delicious, moist and the mousse on top was definitely the best part!! Loved it and it will be my go to when I’m craving chocolate! Thank you for a nice recipe
Kate says
Thank you! I’m so glad that you enjoyed it! Thank you for coming back to leave a comment. =)