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!
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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
ayesha a says
i love this recipe, it looks super delicious! i do have one concern though. i cannot eat marshmallows, are they necessary and/or is there is a substitute? thank you :)
Kate says
Sorry, but they are necessary. The marshmallows provide a lot of the structure for the mousse, and I’m not aware of any easy subs.
Saima says
you can use marshmallow fluff! 1/2 of a regular 7-oz jar
Kate says
Thanks! That’s really helpful. Thanks for commenting! =)
Eugenia Anderson says
Is the cake taken out of pan before frosted?
Kate says
No, the cake is frosted right in the pan.
joy says
hi.i plan to make this.so if the cake is frosted in the pan,should i use spring form pan to bake?so i could just put the mousse on the top?
Kate says
Hi! I wouldn’t recommend using a springform pan. I’ve only seen 9-inch and 10-inch pans, and those wouldn’t be large enough to accommodate the batter for this recipe. The cake that you see pictured with this recipe was topped with mousse in the pan, and then I sliced the cake to take pictures (and serve).
Laura Zurel says
I made this and it was wonderful. My question is, is the batter suppose to be so thin, like water? I double checked my ingredients and all was accounted for.
Thank you
Kate says
I’m glad you liked it! =) The hot water does thin the batter out quite a bit, so, yes, it is a thin cake batter.
Brittany CAMPBELL says
Is the hot water necessary? What does it do to the recipe? About to make this!!
Kate says
Yes, it’s necessary. =) The hot water helps to intensify the chocolate flavor when it mixes with the cocoa powder.
Delectable Tastes says
How essential are the marshmallows and do you have a recommendation for substituting them? A family member doesn’t like them so it would be great to substitute if possible.
Kate says
They’re pretty essential because they provide a lot of the structure for the mousse. There isn’t an easy swap that I know of. Is it just a matter of taste? The mousse doesn’t taste like marshmallows at all.
Maria says
I made 1/4 of the recipe just to see how it would turn out and wouldn’t be a waste of Ingredient s incase it was not so good… well it’s safe to say this was amazing … hands down one of the best things I have made.. :) very Moist and soft cake just perfect ?? Thank you for shearing the recipe
Wanted to ask you if I did a vanilla version what would I substitute the coco powder in the cake with?
Kate says
Thank you! I’m not sure how it would come out, but you can sub cocoa powder with flour. It isn’t a 1:1 substitution, though. You would also want to increase the vanilla, and probably play around with it a bit. Good luck!
Roucksana says
Can vegetable oil be replaced by melted butter?
Kate says
That usually works just fine in cakes. I haven’t tried it in this recipe to say how it will work, though. You’ll just want to adjust the ratio if you sub butter for the vegetable oil (i.e. for every 3/4 cup of veg oil, you’ll need 1 cup of butter).
Brenda Krachenberg says
I have a question maybe related to folding in egg whites and whipped heavy cream.
I make pie filling that starts with a hot custard into which you dissolve unflavored gelatin powder which has been dissolved in water. Then you fold in the beaten egg wites and whipped cream. But when I cut into the pie after refrigeration there,s always a thin layer of colorless gelatin at the bottom. What am I doing wrong?!
Kate says
Hmmmm! My best guess would be that the gelatin isn’t fully dissolving, and then it’s settling into a layer. Usually, when you work with unflavored gelatin, it will say that you have to separate the granulates by sprinkling them either over a cold liquid or with sugar. Then, you mix in boiling water to fully dissolve. Is there a liquid in the recipe that you could mix the gelatin in with before you add the hot water?
Jann says
Yummmmmm! I’m wondering if you’ve tried coffee in place of hot water …
Kate says
I haven’t, but I know people who swear by replacing water with coffee to enhance the chocolate flavor. The closest that I’ve come is replacing water with hot chocolate, which worked nicely.
Cindy says
I was wondering if I could make cupcakes instead of a cake. How many cupcakes would it make and how many minutes would I cook them ?
Kate says
I haven’t ever made this cake into cupcakes. Usually, a 9×13 cake recipe will yield 24 cupcakes, but since I haven’t made it, I can’t say for sure.
Jutta laurino says
Can i make this cake 1 day ahead
Kate says
Yes, the cake keeps well in the fridge.
Esther says
In step 5 of the mouse instructions, what do you mean when you say, “fold whipped cream into. . “
Kate says
Folding is a more gentle way of incorporating ingredients. Rather than mixing or beating to incorporate the ingredients, folding allows you to add ingredients like beaten egg whites or whipped cream without losing all of the volume you just created by beating the egg whites/cream. You can google “folding recipe” and find some good videos that illustrate the technique well.
jane blumberg says
how far in advance can you make this cake? thx
Kate says
I would say 1-2 days should be ok.
Toni Williams says
This looks so yummy! I’m going to make it tomorrow for my Anniversary. When you beat the whipping creme and vanilla together, do you beat until you get soft peaks? Thanks!
Kate says
Thank you! And Happy Anniversary! Yes, you’ll want it at soft peak stage. I’ll make a note of that in the recipe so that it’s more clear.
Diane says
Seems like too much sugar and oil. Can it be reduced ?
Kate says
First, let me preface this by saying that this is chocolate mousse cake, so it’s not health food. If you’re looking for a healthy (or even healthy-ish) dessert, this isn’t that recipe, and I would suggest my Chocolate Buttermilk Bundt Cake instead.
The amount of oil really isn’t that much for a cake of its size. If you significantly cut the amount of oil or sub the oil with something like applesauce, it’s going to change what you end up with. Applesauce, for instance, is going to give you a gummier cake. If you’re ok with that, then give it a shot.
As far as the sugar goes, you could safely cut 1/4 cup or so. If you’re looking to significantly cut the amount of sugar, you’re going to change the structure and taste of the cake, and I wouldn’t recommend doing that.
Danielle says
Does the icing thicken while in fridge cause the icing was pretty liquidy after I added the whipping cream. I just put in fridge so I’m hoping it turns out okay.
Kate says
It is pretty soft initially, but it sets up quite a bit after it has chilled. When you say that you added the whipping cream, do you mean that you added in the straight liquid whipping cream or the beaten whipped cream? That would definitely make a difference in how the mousse comes out.
Kelly says
Can this be made into a layer cake?
Kate says
I would guess so. I haven’t tried it with this cake, but a 9×13-inch sheet cake can usually be made in 2 9-inch round cake pans instead. As a heads up – the mousse is pretty soft initially, so you may need to adjust how you frost and fill the cake.
Kelly says
Than
Karen says
Can I make my own buttermilk for this using vinegar and milk?
Kate says
Yes, that should be fine.
Nicole says
Just finished making this cake and it’s the bomb yo.
Kate says
Thanks!! I’m so glad you liked it!! =D
Donna says
I think this will make me a very happy person soon! lol
Kate says
I hope so! =)
Karen says
I assume this cake needs to be kept in the refrigerator?? It looks really yummy.
Kate says
It does need to be kept in the fridge. I’ve made a note of that. Thanks!!