This chocolate mousse cake is absolute chocolate HEAVEN! Three layers of chocolate are all wrapped up in one delicious dessert – it starts with a moist chocolate cake base that’s piled high with light chocolate mousse. Once chilled, the entire cake is covered in a layer of rich chocolate ganache. Each bite just melts in your mouth with so many different levels of delicious chocolate flavor.
Rich chocolate cake
Of course it wouldn’t be a chocolate mousse cake recipe without a rich and decadent chocolate cake!
The base of this recipe is a moist and spongy chocolate cake that’s very easy to make. Simply whisk together oil, sugars, eggs, vanilla, and sour cream. Then mix in the dry ingredients followed by hot coffee to activate the dry cocoa powder.
A few key ingredients are included to produce the perfect cake layer base:
- Cornstarch – A tiny bit of cornstarch is all that’s needed to create a tender and soft chocolate cake.
- Dutch Cocoa – This cocoa is much darker with a smoother flavor compared to regular unsweetened cocoa. It makes any cake look and taste gourmet.
- Sour Cream – I absolutely LOVE sour cream in chocolate cake! It makes the overall texture so rich and the acidity helps balance out the flavors.
- Hot Coffee – Coffee pairs perfectly with chocolate, and using hot coffee will activate the dry cocoa powder within the batter. Without the heat, the cocoa flavor be as strong.
Once the cake has baked and cooled, two additional steps are needed:
- Level – The very top of the cake is sliced off to create a level base. This also exposes a porous surface which is necessary for step two.
- Soak – Once leveled, a mixture of cocoa and hot coffee are spooned over the surface of the cake. The cake absorbs this moisture to create a INCREDIBLY moist and tender consistency. This step is optional, but it is most definitely well worth it.
How to make chocolate mousse
Get your bowls cleaned and ready because we will be using a lot of dishes! And while there are many steps to make chocolate mousse, each one is very simple.
Step 1 – Chocolate
To make a chocolate mousse that isn’t too bitter or too sweet, my recipe uses equal parts dark and milk chocolate. Go for a 70% cocoa dark chocolate as it provides tons of rich chocolate flavor without any bitterness. Also use good quality chocolate as this will make a BIG difference in the overall flavor. I linked my favorites in the recipe card below.
These two chocolates are chopped and slowly melted in a bowl over simmering water. Once melted, the chocolate rests for a couple minutes to cool slightly.
After those few minutes, egg yolks are whisked into the chocolate mixture one at a time. Raw egg is needed in chocolate mousse to create a rich and creamy consistency.
Step 2 – Gelatin
Gelatin is one of the ingredients that helps the mousse set once chilled. To incorporate the gelatin, it first needs to bloom.
To do so, sprinkle unflavored gelatin powder over a small dish filled with water. The gelatin will absorb the water and “bloom” – aka turn gelatinous and clear.
In the meantime, heat a pot of heavy cream just until it’s steaming. Then the bloomed gelatin is whisked and melted in. The cream acts as the vehicle to transport the gelatin smoothly. It also adds an extra layer of richness to the mousse.
The hot gelatin cream is slowly whisked into the bowl of chocolate and egg yolk.
Step 3 – The Fluff
Not an official term, but a term nonetheless! This refers to the ingredients that add lightness and “fluff” to the mousse.
First, heavy cream is whipped until it reaches stiff peaks.
The, egg whites are whipped along with cream of tartar and sugar to create a fluffy meringue.
The two are individually folded into the bowl of chocolate. To fold, use a rubber spatula and run it around the mousse and through. This process takes some time, but it’s important to gently mix, otherwise the mousse will deflate and turn into chocolate fudge.
How to assemble chocolate mousse cake
The cake has cooled and soaked and the mousse is ready to go so now it’s time to assemble our chocolate mousse cake!
First, the chocolate cake pan is lined with a sheet of acetate to create a cake collar. This will hold in the mousse and make for clean sides once the cake has chilled.
Slide the acetate down the sides of the pan until it reaches the bottom, nudging it between the cake and the pan wall.
Then pour the mousse over the cake. It will fill all the way to the top of the springform pan so it’s important that the cake collar reaches about an inch above the pan.
The mousse cake then chills for at least 4 hours but preferably overnight. It’s a thick layer of mousse so overnight ensures that it’s set all the way through.
Chocolate ganache recipe
Now comes the final layer – the chocolate ganache! When the chocolate mousse cake has chilled, release the ring and peel bag the cake collar. This process is so very satisfying.
Then to make the ganache, pour very hot cream over a bowl of chopped dark chocolate. The cream will slowly melt the chocolate after about 3 minutes. Use a whisk to mix the two together to create a smooth and glossy ganache.
Pour the ganache in the very center of the cake. Then use a small offset spatula to nudge it to the sides and over the edge of the cake. This will create those gorgeous cake drips.
Chill the mousse cake for at least 30 minutes, just until the ganache is set, and our trip chocolate mousse cake is ready to eat!
Chocolate Mousse Cake FAQs
Yes! The entire cake is gluten free minus the flour in the cake batter. Simply swap it with a cup for cup gluten free baking flour.
Dutch process cocoa is not as acidic as unsweetened cocoa. For this reason, subbing in regular unsweetened cocoa could throw off the leaveners and create a completely different texture.
You can, but dark brown sugar adds an extra layer of moisture that light brown sugar just doesn’t quite achieve.
If you don’t like the flavor of coffee, don’t worry! You can’t taste it, it just helps elevate the chocolate flavors. Decaf can also be used if caffeine is a concern. Otherwise, sub in hot water instead.
Using a mix of dark and milk chocolate lends the best flavor as it’s not too bitter and not too sweet. For dark chocolate, use a 70% cocoa dark chocolate. Also opt for good quality chocolate as this will provide the biggest flavor payoff. I’ve linked the ones I use in the recipe card below.
Unfortunately this only works with a springform pan. The cake is nearly impossible to release or slice into if it’s in a pan without a removable bottom.
Once the ganache is added, the cake chills for 30 minutes. Then it’s ready to serve! If your plans require the cake to chill for longer, allow the mousse cake to sit at room temperature for about 30 minutes before serving.
Store the cake in an airtight container in the refrigerator. It will keep for about a week.
For more decadent chocolate desserts, check out my:
- Moist Chocolate Cake
- Brown Butter Brownies
- Flourless Chocolate Cake
- Salted Dark Chocolate Brownies
- Brownie Pie
- Peanut Butter Chocolate Cake
Make sure to tag me @butternutbakery on Instagram and comment below if you make this chocolate mousse cake. To pin this recipe and save it for later, you can use the button on the recipe card or on any of the photos above. Happy baking!Print