Chocolate Mousse Cake Recipe

I made a Fluffy Chocolate Mousse layered on moist chocolate cake with chocolate whipped cream, and I reveal the one unexpected trick that makes this indulgent dessert so easy to pull off.

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I’m calling this my Decadent Chocolate Mousse Cake because it almost feels illegal. Layers of moist chocolate cake, airy chocolate mousse and a cloud of chocolate whipped cream collide into something that melts on your tongue.

I swear the trick is the deep bittersweet chocolate and a good hit of unsweetened cocoa powder, they make everything sing. I messed up the first time, left the mousse too warm and it slumped, but that mistake taught me the texture you actually want.

If you like intense chocolate and a little drama, you’re gonna want to keep reading. Trust me.

No regrets.

Ingredients

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All purpose flour: mostly carbs, provides structure, not much fiber or protein, kinda plain.
Unsweetened cocoa: rich in antioxidants, adds deep chocolate flavor, slightly bitter, low sugar.
Granulated sugar: pure carbs, makes cake sweet, no nutrients, use sparingly if you care.
Eggs: add protein and moisture, help set crumb, give richness and color.
Heavy cream: high fat, creates silky mousse and stable whipped cream, adds richness.
Bittersweet chocolate: provides intense cocoa flavor, adds fat and some antioxidants, bittersweet balance.
Vanilla extract: tiny flavor boost, smells amazing, doesn’t add nutrition, just makes it feel fancy.

Ingredient Quantities

For the chocolate cake
- 1 3/4 cups (220 g) all purpose flour
- 3/4 cup (65 g) unsweetened cocoa powder
- 2 cups (400 g) granulated sugar
- 1 1/2 tsp baking powder
- 1 1/2 tsp baking soda
- 1 tsp salt
- 2 large eggs room temp
- 1 cup (240 ml) whole milk room temp
- 1/2 cup (120 ml) vegetable oil
- 2 tsp vanilla extract
- 1 cup (240 ml) boiling water or hot coffee

For the chocolate mousse
- 12 oz (340 g) bittersweet or semisweet chocolate chopped
- 1/2 cup (120 ml) heavy cream hot
- 1 1/2 cups (360 ml) heavy cream cold for whipping
- 3 tbsp powdered sugar
- 1 tsp vanilla extract
- pinch of salt

For the chocolate whipped cream
- 1 1/2 cups (360 ml) heavy cream cold
- 1/3 cup (35 g) unsweetened cocoa powder sifted
- 1/2 cup (60 g) powdered sugar
- 1 tsp vanilla extract

Optional garnish
- 2 oz (50 g) chocolate shavings or curls
- cocoa powder for dusting
- fresh berries like raspberries or strawberries optional

How to Make this

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1. Preheat oven to 350 F (175 C). Grease and line two 9 inch round pans with parchment and dust with flour. In a large bowl whisk together 1 3/4 cups (220 g) all purpose flour, 3/4 cup (65 g) unsweetened cocoa powder, 2 cups (400 g) granulated sugar, 1 1/2 tsp baking powder, 1 1/2 tsp baking soda and 1 tsp salt. Tap the bowl so it looks messy like real life.

2. In another bowl beat 2 large eggs room temperature, 1 cup (240 ml) whole milk room temperature, 1/2 cup (120 ml) vegetable oil and 2 tsp vanilla until blended. Pour wet into dry and mix until just combined, do not overmix or the cake gets tough.

3. Stir in 1 cup (240 ml) boiling water or hot coffee slowly, batter will be thin, that is correct. Divide between the prepared pans, tap pans on counter to remove bubbles and bake 30 to 35 minutes or until a toothpick comes out with a few moist crumbs. Cool 10 minutes in pans, then remove to a rack and cool completely.

4. Make the chocolate base for the mousse. Put 12 oz (340 g) chopped bittersweet or semisweet chocolate in a heatproof bowl. Pour 1/2 cup (120 ml) hot heavy cream over the chocolate, let sit 1 minute then whisk until smooth. If it looks too loose chill 5 to 10 minutes, it should be thick but still spreadable.

5. Chill your mixing bowl and whisk for 10 minutes if you can. Whip 1 1/2 cups (360 ml) cold heavy cream with 3 tbsp powdered sugar and 1 tsp vanilla to medium peaks. Fold about one third of the whipped cream into the cooled chocolate to loosen it, then gently fold in the rest with a pinch of salt until light and fluffy. Do not beat or it will deflate.

6. Assemble the cake. If you have two layers place one layer on your serving plate, spread the chocolate mousse evenly over it, then top with the second layer. If you only made one layer slice it horizontally and use the same method. Scrape the sides clean for a nice look or be messy if you want, no judgement.

7. Refrigerate the assembled cake for at least 3 hours or overnight so the mousse firms up and the flavors meld. This is important for texture.

8. Make the chocolate whipped cream right before serving. Chill the bowl and whisk again if possible. Whip 1 1/2 cups (360 ml) cold heavy cream with 1/3 cup (35 g) sifted unsweetened cocoa powder, 1/2 cup (60 g) powdered sugar and 1 tsp vanilla to stiff peaks. Taste and adjust sugar if you like it sweeter.

9. Spread or pipe the chocolate whipped cream over the chilled mousse layer, garnish with 2 oz (50 g) chocolate shavings or curls and a light dusting of cocoa powder. Add fresh berries like raspberries or strawberries if you want brightness. To slice, dip a sharp knife in hot water and wipe between cuts for clean pieces.

10. Serve cold or just slightly less cold, store leftovers covered in the fridge up to 3 days. If the mousse seems a bit loose the next day it will still taste amazing so don’t panic if it looks imperfect.

Equipment Needed

1. Oven (preheat to 350 F, 175 C)
2. Two 9-inch round cake pans, parchment paper and flour for lining
3. Mixing bowls (one large for dry, one medium for wet)
4. Measuring cups, spoons and a kitchen scale (grams help a lot)
5. Whisk plus an electric hand mixer or stand mixer with whisk attachment
6. Heatproof bowl and small saucepan or microwave-safe jug to heat cream and melt chocolate
7. Rubber spatula and an offset spatula for spreading the mousse neatly (or not, your call)
8. Cooling rack
9. Serrated knife for slicing layers and a sharp knife or grater for chocolate shavings

FAQ

Q: Can I use hot coffee instead of boiling water in the cake batter? A: Yes, absolutely. The hot coffee deepens the chocolate flavor and you can use decaf if you don't want caffeine, just pour it in hot so it blooms the cocoa but don't overthink it, the batter will be thin and that's normal.

Q: How do I get a light but stable chocolate mousse? A: Melt the chopped chocolate with the hot 1/2 cup cream to make a smooth ganache, let it cool to warm, whip the cold cream to soft-medium peaks, then fold gently so you don't knock out the air; chill at least 1-2 hours to set. For extra stability add 1 tsp powdered gelatin (bloom in 2 tbsp water, dissolve into warm ganache) or use the powdered sugar in the whipping cream and keep everything cold.

Q: My mousse looks runny or curdled, how do I fix it? A: If the chocolate was too hot it can thin the whipped cream, so cool the ganache then chill the bowl and re-whip some cold cream to soft peaks and fold in slowly. If the chocolate seized, add a little more hot cream and whisk to smooth, or refrigerate and re-emulsify before folding. Gelatin can rescue texture if needed.

Q: Do I have to cool the cake layers before spreading the mousse? A: Yes, you must. Warm cake will melt the mousse and make the whole cake sag, so cool layers to room temp and ideally chill them briefly before assembling.

Q: How should I store or make the cake ahead? A: You can bake the layers a day or two in advance, wrap well and keep in the fridge or freeze layers up to 2 months. Assembled cake keeps 2-3 days in the fridge, or freeze whole cake up to 1 month and thaw overnight in the fridge.

Q: Any tips for clean slices and nice presentation? A: Chill the cake well before cutting, use a sharp knife warmed under hot water and wiped dry between slices, top with chocolate shavings or a dusting of cocoa and add berries for contrast, it's simple but it looks fancy.

Chocolate Mousse Cake Recipe Substitutions and Variations

For whole milk
- Buttermilk: use 1 cup buttermilk or make 1 cup by adding 1 tbsp vinegar or lemon juice to milk and let sit 5 min, gives a tender, slightly tangy crumb.
- Non dairy milk: almond, soy or oat milk + 1 tbsp vinegar to mimic buttermilk for 1 cup. It’s lighter and changes flavor a bit.
For vegetable oil
- Melted unsalted butter: swap 1 cup oil for 1 cup melted butter, adds richer flavor, cool slightly before mixing.
- Neutral coconut oil or half applesauce: use equal coconut oil (melt first), or replace up to half the oil with applesauce to cut fat but cake will be a bit denser.
For bittersweet chocolate (mousse)
- Semisweet or 70% dark chocolate: same weight, semisweet is sweeter, 70% gives more intense chocolate.
- Cocoa powder + butter: combine 3 tbsp unsweetened cocoa + 1 oz butter to roughly replace 1 oz chopped chocolate, adjust sugar to taste.
For heavy cream (whipping or mousse)
- Chilled full fat coconut cream: refrigerate cans overnight, scoop solid cream and whip — great dairy free option but expect coconut flavor.
- Mascarpone + milk: blend 3/4 cup mascarpone with 1/4 cup milk to mimic richness when you can’t whip enough cream, it’s thicker so fold gently.

Pro Tips

1. Use hot strong coffee instead of plain boiling water to bump up the chocolate flavor; if you dont want caffeine, decaf works great too.

2. Chop the mousse chocolate very fine and pour the hot cream over it, then let it sit a minute before whisking so it melts smoothly; if it looks grainy or split, add a spoonful of hot cream and whisk to bring it back together.

3. If you need extra stability in warm weather, bloom 1 tsp unflavored gelatin in 2 tbsp cold water, melt gently and whisk into the warm chocolate base before folding in whipped cream; it keeps the mousse firm without changing the taste.

4. Chill your bowl and beaters and whip slowly at first, then increase speed; stop the mousse at medium peaks and the whipped cream at stiff peaks. If you overbeat the mousse a bit, gently fold in a few tablespoons of fresh whipped cream to revive it.

5. For neater slices and better flavor, chill the assembled cake for several hours, then bring it out 10 to 20 minutes before serving so the mousse softens slightly; use a hot knife wiped between cuts for clean edges.