This Chocolate Mousse Cake is the perfect cake for chocolate lovers. It's a delicious, rich and creamy dessert cake that suits any occasion. It consists of a chocolate cake layer filled with chocolate mousse and topped with chocolate ganache. Doesn't that sound irresistible? By the way, have you tried my chocolate cream pie yet?
Step-by-step video tutorial
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Expert tips for success
- Measure the flour and cocoa powder correctly for the chocolate cake layer. If you're not using a kitchen scale, fluff the dry ingredient up, then scoop it into the measuring cup and level with the back of a knife without packing. If you don't measure the dry ingredients correctly, the cake layer can become dry and hard.
- Be careful not to overbake the cake layer. It's very thin and overbakes quickly.
- Allow the cake base to cool completely before filling it with the chocolate mousse.
- Do not boil the egg yolk mixture at any point or you could end up with either scrambled eggs or the chocolate custard splits.
- Use only high-quality chocolate bars for the mousse instead of chocolate chips. Otherwise the chocolate custard base for the mousse could become grainy and crumbly.
- Stop folding the whipped cream into the chocolate custard as soon as it is combined. Don't overmix it or it won't set properly.
- Make sure you chill the cake in the fridge for at least 4 hours before serving as it needs time to set and chill properly. Do not put it in the freezer to speed up the cooling process.
Chocolate mousse troubleshooting
Why did my chocolate custard split?
If the chocolate splits and you have an oily film on the surface, then the chocolate got too hot too quickly. Make sure to remove the egg custard from the heat first, continue beating for about 1-2 minutes, then stir in the chocolate.
How to fix it?
- If this has happened to you, the first thing you should do is grab your electric mixer and blend until everything comes together. In most cases this will work just fine and save your chocolate mousse. It becomes smooth and silky again.
- If that didn't help at all, heat 1-2 tablespoons (15-30 ml) of whipping cream and gradually stir into the custard. Stop adding cream once it comes together. Normally that should help.
Why is my mousse runny and not setting?
If your chocolate mousse is runny, there can be a couple of reasons. First, the custard hasn't been cooked long enough. Second, the whipped cream wasn't stiff enough.
How to avoid this?
- Be sure to cook the egg custard long enough for it to thicken and coat the back of a spoon.
- When folding the whipped cream into the chocolate cream, be careful not to destroy any air pockets. Do not overwork the mousse. Also, don't use low-fat whipping cream.
Can I make the cake layer with natural cocoa powder?
The cake layer is made with dutch-processed cocoa powder and baking powder. If you want to use natural unsweetened cocoa powder, substitute the cocoa powder 1:1. Instead of 1 ½ teaspoon of baking powder, use ¾ teaspoon baking powder and ¼ teaspoon of baking soda.
How do I make hot cocoa needed for the cake layer?
Hot cocoa is just unsweetened cocoa powder and boiling hot water. You typically need 1 teaspoon of cocoa powder per ¼ cup (60 mL) of water, but you can check the package directions to see if there is any. Do not use hot chocolate or sweetened cocoa as this would change the texture and flavor of the cake layer. Alternatively, use hot water for the cake and add an extra teaspoon of cocoa powder to the batter.
Can I freeze it?
I don't recommend freezing chocolate mousse cake because it changes its texture during the freezing and thawing process. Also, it can be that ice crystals develop within the air pockets and when thawing they melt and make the mousse watery.
More chocolate cake recipes to try
- Black Forest Cake
- Chocolate Layer Cake
- Triple Chocolate Ombré Cake
- Peanut Butter Chocolate Cake
- Texas Sheet Cake
- Flourless Chocolate Cake
Recipe
The Chocolate Mousse Cake Recipe
Ingredients
Chocolate mousse
- 3 cups heavy whipping cream, divided
- 8 large egg yolks
- ¼ cup granulated white sugar
- 18.5 oz high-quality semi-sweet chocolate bars, melted
- ¾ cup powdered sugar, sifted
Chocolate cake layer
- 1 cup all-purpose flour, spooned and leveled
- ⅜ cup dutch-processed cocoa powder, spooned and leveled
- ¾ cup granulated white sugar
- 1 ½ teaspoon baking powder
- ½ teaspoon salt
- ¼ cup mild vegetable or canola oil
- 1 large egg
- ¼ cup buttermilk
- 1 teaspoon vanilla extract
- ¼ cup hot cocoa (unsweetened beverage)
Chocolate glaze
- 6 oz high-quality semi-sweet chocolate, finely chopped
- ¾ cup heavy whipping cream
Instructions
- Make the chocolate mousse: In a medium saucepan, whisk together 1 ½ cups heavy cream, egg yolks, and sugar and cook over medium-high heat, until it thickens and coats the back of a spoon, about 1-2 minutes. Whisk continuously. Remove from the heat and continue whisking for about 1-2 minutes. Add melted chocolate and whisk until combined. Transfer the chocolate custard to a large mixing bowl and let cool completely.
- Preheat the oven to 350°F/175°C. Line the bottom and the sides of a 9" / 23cm baking pan with parchment paper and set aside.
- Make the chocolate cake layer: In a medium-sized bowl, mix together the flour, cocoa, sugar, baking powder, and salt and set aside. In a large mixing bowl, using an electric mixer fitted with a whisk or paddle attachment, beat the oil, egg, buttermilk and vanilla, just until combined. Stir in dry ingredients to combine. Slowly mix in the hot cocoa until well combined. The batter will be thin. Pour the batter into the prepared baking pan and bake 14-18 minutes or until a toothpick inserted into the center comes out clean. Leave to cool in the pan for about 20 minutes. Then open the springform pan and let it cool down to room temperature.
- Continue with the chocolate mousse: In a large mixing bowl, using an electric mixer fitted with a whisk attachment, beat the remaining 1 ½ cups heavy whipping cream until soft peaks form. Add powdered sugar and beat until stiff peaks form.
- Using a whisk, stir about ¼ of the whipped cream into the cooled chocolate cream until smooth and combined. Then carefully fold the remaining whipped cream into the chocolate mixture with a spatula until combined. Don't overwork the mousse or it won't set properly.
- Assemble the cake: Slice a thin layer from the top of the cooled cake layer to create a flat surface if needed. Attach the springform ring and close the pan. Then carefully pour the chocolate mousse into the pan and spread evenly. Chill in an airtight container in the refrigerator overnight.
- Make the chocolate ganache: Place chopped chocolate in a large heatproof bowl and set aside. Place heavy cream in another heatproof bowl and microwave until very hot, almost boiling, about 1-2 minutes. Pour over the chocolate and let stand 1-2 minutes. Whisk until smooth and the chocolate has completely melted. Chill in the fridge for about 10-15 minutes to thicken. Test the consistency of the ganache on the side of the bowl. It should drip. The longer it cools, the thicker it gets. If it's too firm, reheat it in the microwave for a few seconds. Once it has reached the desired consistency, it can be spooned onto the cake.
- Remove the ring from the springform pan and gradually spoon the ganache around the edges of the cake, letting it drip down the sides. Do this with a small spoon, making a drop at a time. Then spoon or pour the rest of the frosting onto the cake (you may not need all of it) and smooth with an offset spatula. Place the cake in the fridge for 15 minutes to allow the ganache to set. Decorate as you like. Store in an airtight container in the refrigerator for up to 3 days.
Video
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Stacey
I'm making this right now, I used a brownie base instead of cake, I didn't realize that I had to leave it overnight to set, has anyone tried putting in the freezer? How long do you think it would take to set in the freezer?
Sabine
I'm sorry, I've never tried to let it set in the freezer. I'm not sure if the texture would be the same as when chilled overnight.
Susie L.
WOW! I've never felt compelled to leave a review, but then I made this cake! Perfect texture and taste! Many family birthdays have been celebrated with a run to a local French bakery to pick up a chocolate mousse cake. The bakery will miss us!
Thank you for sharing!