Chocolate Mousse Cake
This chocolate mousse cake layers moist chocolate cake, coffee-cocoa soak, airy chocolate mousse, and glossy ganache for a chilled dessert that slices cleanly.
About This Recipe
Chocolate mousse cake needs two kinds of patience: letting the cake cool and letting the mousse set. Those resting times are what give the dessert its clean layers.
This version keeps the process organized: bake the cake base, add the coffee soak, fold the mousse gently, chill until firm, then finish with ganache.
Ingredients
- ✓3/4 cup (95g) all-purpose flour (or gf baking flour)
- ✓2 tbsp cornstarch
- ✓1/4 cup (25g) dutch process cocoa powder
- ✓1 tsp baking soda
- ✓1/2 tsp baking powder
- ✓1/4 tsp kosher salt
- ✓1/2 cup (100g) fine granulated sugar
- ✓1/2 cup (105g) dark brown sugar, packed
- ✓1/2 cup (112g) vegetable or olive oil
- ✓2 large eggs
- ✓1 tsp vanilla extract
- ✓1/2 cup (120g) sour cream
- ✓1/2 cup (120g) hot coffee
- ✓1/2 cup (120g) hot coffee
- ✓1 tbsp dutch process cocoa powder
- ✓7 oz 70% dark chocolate, chopped
- ✓7 oz milk chocolate, chopped
- ✓3 large eggs, separated
- ✓3 tbsp water
- ✓1 1/2 tsp unflavored gelatin
- ✓1 3/4 cup heavy cream, divided
- ✓1/2 tsp cream of tartar
- ✓1/4 cup (50g) fine granulated sugar
- ✓6 oz 70% dark chocolate, chopped
- ✓3/4 cup (180g) heavy cream
Ingredient Notes
- Chocolate: Use chocolate you enjoy eating because it drives the mousse and ganache flavor.
- Gelatin: Bloom it fully so the mousse sets without rubbery bits.
- Heavy cream: Whip only to soft or medium peaks so it folds smoothly.
- Coffee soak: Coffee deepens chocolate flavor without making the cake taste like coffee.
Instructions
- 1
Heat the oven to 350°F and prepare a 9-inch springform pan with parchment.
- 2
Whisk the dry cake ingredients in one bowl and the sugars, oil, eggs, vanilla, and sour cream in another.
- 3
Combine the mixtures, stir in the hot coffee, and bake until the cake is set. Cool completely.
- 4
Level the cooled cake and return it to the clean springform ring with a cake collar or parchment strip.
- 5
Brush or spoon the coffee-cocoa soak over the cake layer.
- 6
Melt the chocolate for the mousse and let it cool slightly.
- 7
Bloom the gelatin, warm the cream, and combine it with the chocolate mixture until smooth.
- 8
Whip the remaining cream, then gently fold it into the chocolate mixture.
- 9
Spread the mousse over the cake and chill until firm.
- 10
Pour ganache over the set mousse and chill again until sliceable.
- 11
Unmold carefully, slice with a warm knife, and serve chilled.
Katy’s Kitchen Tips
- Use a cake collar or parchment strip for clean sides.
- Cool the cake completely before adding mousse.
- Fold whipped cream gently to keep the mousse airy.
- Chill until fully set before adding ganache or slicing.
Variations and Substitutions
- Espresso finish: Add a little espresso powder to the ganache.
- Berry topping: Serve with raspberries or strawberries for brightness.
- Dark chocolate: Use more dark chocolate for a less sweet cake.
- Neat slices: Warm and wipe the knife between cuts.
What to Serve With Chocolate Mousse Cake
Serve chilled with whipped cream, fresh berries, coffee, or a light dusting of cocoa powder.
Storage and Reheating
Refrigerate covered for up to 4 days.
Freeze individual slices well wrapped, then thaw overnight in the refrigerator.
Common Mistakes to Avoid
- Warm cake layer: Mousse can melt or slide if the cake is not cool.
- Overwhipped cream: Stiff cream is harder to fold smoothly.
- Skipping chill time: The mousse needs time to set before slicing.
- Hot ganache: Ganache that is too warm can soften the mousse layer.
FAQ
Can I make chocolate mousse cake ahead?
Yes. It is best made at least several hours ahead so the mousse can set.
Why did my mousse layer turn dense?
The chocolate may have been too hot or the whipped cream may have been folded too aggressively.
Do I need a springform pan?
A springform pan or cake ring makes unmolding much easier.
How should I slice it cleanly?
Use a warm knife and wipe it between cuts.
Nutrition Facts
- Serving Size: 1 serving