This is the perfect Chocolate Mousse Cake recipe. The thin and soft chocolate cake layer is topped with a super creamy chocolate mousse and soft chocolate ganache. It's a delicious, rich, and creamy chocolate dessert cake that fits every occasion. To make sure that you can replicate this recipe with success, I provide you with a step-by-step video, and I talk more in-depth about making chocolate ganache since this is the most crucial part that your cake is a success. By the way, did you try my silky chocolate cream pie yet?
Chocolate Ganache Troubleshooting
To make the chocolate mousse filling you need to make a chocolate ganache first that is the base of the mousse. The chocolate ganache is the trickiest part of the whole recipe. At the point, when you add the melted chocolate to the cooked custard, it can happen that the chocolate splits, gets grainy, or you have an oily film on the surface. This can happen when the chocolate is getting too fast too hot. So make sure that you remove the pan from the heat first, continue whisking, and then add the chocolate.
So, what can you do if the chocolate splits? Do you need to throw everything away and start new? Generally, no. Here are my troubleshooting tips:
- The first thing you should do is to grab your electric mixer and mix until it comes together. In most cases, this will work fine and saves your ganache. It will be smooth and silky again.
- If this didn't do the trick already, mix in 1 tablespoon (15ml) of corn syrup or honey to smooth it.
- If this didn't help either, heat 1-3 tablespoon (15-45ml) heavy cream until hot and stir it into the ganache little by little. Normally, this should help.
What is if your ganache is still broken? Well then you have to face the truth that the chocolate was way too hot, and you better do it again. Did this ever happen to me? Of course! Multiple times. The most important thing: Keep calm. In most cases, you can fix it very easily. And if not? Go on and do it again. With practice, you get better, and you learn from mistakes. I found a great article on how to fix a broken ganache.
If you did everything right (or fixed it) the ganache will look like in the picture below.
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The Chocolate Mousse Cake Recipe
Ingredients
Chocolate mousse
- 3 cups heavy cream, divided (720ml)
- 8 large egg yolks
- ¼ cup granulated white sugar (50g)
- 3 cups semi-sweet chocolate, melted (525g)
- ¾ cup powdered sugar, sifted (90g)
Chocolate cake layer
- 1 cup all-purpose flour (120g)
- ⅜ cup dutch-processed cocoa powder (32g)
- ¾ cup granulated white sugar (150g)
- 1+½ teaspoon baking powder
- ½ teaspoon salt
- ¼ cup vegetable or canola oil (60ml)
- 1 large egg
- ¼ cup buttermilk (60ml)
- 1 vanilla bean* (or 1 teaspoon vanilla extract)
- ¼ cup hot cocoa (60ml)
Chocolate glaze
- 1 cup semi-sweet chocolate, finely chopped (175g)
- ¾ cup heavy cream (180ml)
Video
Instructions
- Make the Chocolate Mousse: In a medium saucepan, whisk together 1+½ cups heavy cream, egg yolks, and sugar and cook over medium heat for about 1-2 minutes until it coats the back of a spoon. Do not boil at any time. Remove from heat and continue whisking about 1 minute. Add melted chocolate and whisk consistently. Transfer to a bowl and let cool completely. If your chocolate ganache breaks, then read the blog post above to know how to fix the ganache easily.
- Preheat oven to 350°F/175°C. Line the bottom and the sides of a 9" / 23cm baking pan with parchment paper. Set aside.
- Make the chocolate cake layer: In a medium bowl combine flour, cocoa, sugar, baking powder, and salt and stir to combine. Set aside. In a large mixing bowl with a stand or handheld mixer fitted with a whisk or paddle attachment, beat oil, egg, buttermilk, and vanilla* just until combined. Stir in dry ingredients to combine. Slowly mix in hot cocoa until combined. The batter will be thin. Transfer batter to the prepared baking pan. Bake for 16-18 minutes or until a toothpick in the center comes out clean. Don't overbake. I baked mine for 18 minutes. Let cool in the pan for about 20 minutes. Then open the springform pan and let cool to room temperature.
- Continue with the Chocolate Mousse: With a handheld or stand mixer fitted with a whisk attachment, whisk 1+½ cups heavy cream until soft peaks form. Add powdered sugar and whisk until stiff peaks form. Stir about ¼ of whipped cream into the cooled chocolate cream with a whisk. Then gently fold in the remaining whipped cream with a wooden spoon.
- Assemble the cake: Cut a thin layer off the top of your cake to create a flat surface. Close the springform pan again. Spread the chocolate mousse evenly on top of the cake layer. Chill overnight in an airtight container in the fridge.
- Make the chocolate glaze: Place chopped chocolate in a large heatproof bowl. Place heavy cream in another heatproof bowl and microwave until very hot, almost boiling for about 1-2 minutes. Pour over chocolate and let stand 1-2 minutes. Whisk until smooth, and the chocolate is completely melted. Let cool in the fridge for about 10-15 minutes that it thickens. Test the consistency of the glaze down the side of the bowl. It should drip. The longer it stands, the thicker it gets. If it is too firm, re-warm it a few seconds in the microwave. Once it reached the desired consistency, it's ready to spoon on top of the cake.
- Remove cake from the fridge and spoon the glaze little by little around the sides and let drip off the sides. Do this with a small spoon and do one drip at the time. Then spoon or pour the rest of the glaze on top of the cake (maybe you don't need all) and level with an offset spatula. Place cake in the fridge for 15 minutes that the glaze gets firm if needed. Decorate with grated chocolate and berries if desired or to your preference. Store leftovers in an airtight container in the fridge up to 3 days.
Notes
Nutrition
Nate
What kind of hot coco did you make? I find just "hot cocoa" imprecise. There are a lot of different hot cocoas out there. Ones that need hot milk and ones that use hot water. Ones you make out of your Keurig and the consistency depends on how much water you choose to add. I just finished backing the cake layer. It seems to be coming together well so far.
Sabine
I usually use cocoa powder and mix it with hot water. I use about 1-2 tbsp cocoa powder per cup of water. I hope that helps.
Lucy Barr
I'm insure of ⅜ cup dutch-processed cocoa powder (32g) because 32 grams equal 1/4 cup,'
So how much cocoa powder do I use?
Sabine
1 cup of cocoa powder weighs 85g. So 3/8 cup weighs 32g. Please be aware that the weight of 1 cup cocoa powder doesn't equal the weight of 1 cup flour. It sounds to me that you were calculating the weight of flour. You can measure by weight (grams) or volume (cups), whichever suits you better. I hope that helps.
Ziana L Clinton
Turned out wonderful. Can't wait to try it again. Froze the leftovers in individual slices. Worked!
Sandra
Soooo yummy!!!
David
Wonderful and very rich dessert.
I cooked the eggs to a temp of 165 with a candy thermometer to ensure the right texture, instead of the back of a spoon technique.
I wound up making a brownie layer for the base, but I think the cake has cleaner edges.
Very good! Will make again
Trey smith
Hello this is my second time making this recipe. I love making it, just challenging enough to keep you on your toes. This time I made a raspberry cake filling to try between the moose and cake layer. I always have a little extra each time I make it, so I’m making cupcakes. Thank you very much this has reawaken the baker inside me!! P.S let you know how the raspberry filling turns out with it this time.
Chris
Hello,
I am making this with my son and the cake part is extremely thick (fudge like consistency). I double checked all my ingredients were correct and added the right way. Any suggestions ?
Sabine
I'm sorry, I'm not sure what went wrong because it's basically a thin layer of chocolate cake. It never happened to me before so I can't tell what went wrong down the process.
Tom
Credit where credit is due! This is hands-down the best cake recipe I’ve ever tried! And it came out just like it was supposed to.
Melinda
I am making this for my daughter’s birthday. Can you clarify how much cocoa powder you use to make 1/4 cup hot cocoa?
Sabine
You can use 1/2 tbsp of cocoa powder mixed with 1/4 cup hot water. I hope that helps!
Meher Eqbal
Hi Sabine, we tried your mousse cake this weekend, sadly it didn't turn out well for us. It definitely looked the part but taste was not up to par for us. Although I must say through NO fault of your recipe though! I think it was down to the ingredients we used. I think the chocolate we used was too dark and the wrong cream ( UK USA difference) , and had issues with the sponge because of size of egg and hot Chocolate confusion. But I did want to say thank you for the very clear measurements and conversions it definitely made the recipe easy to follow. Just next time I think we will be more careful with Coco content and egg sizes etc. Just wanted to put this as a comment not to criticize, but to warn other people to be very careful with these things too, so to not end up with our problem. ( It turned out too bitter but not the nice kind and generally we do love our bitter chocolates btw) also another thing I think we should have left the cake at room temperature for about half an hour or so before we ate it ( winter time) . Which us impatient lot didn't of course 🤣 so it was more like a truffle 🙈 than a mousse, but nevertheless thank you for a well written clear recipe, the problems were from our side.