I’ve made a lot of chocolate desserts in my life. This one gets the most requests for the recipe.
It’s rich, it’s silky, and it looks like something from a bakery window. But it’s honestly not that complicated once you know the order of operations.
I make this for birthdays, dinner parties, and one time just because it was raining and I wanted cake. No regrets there either.
Side Note: If you love rich Latin desserts too, you might like these Brazilian brigadeiros I fell for during a cooking class in Florianópolis.
What You’ll Need
For the chocolate cake base:
- 1 cup all-purpose flour
- 1 cup granulated sugar
- ½ cup unsweetened cocoa powder
- 1 tsp baking soda
- ½ tsp baking powder
- ½ tsp salt
- 1 large egg
- ½ cup buttermilk
- ½ cup vegetable oil
- 1 tsp vanilla extract
- ½ cup hot coffee (or hot water)
For the chocolate mousse layer:
- 8 oz semisweet chocolate, chopped
- 2 cups heavy whipping cream, divided
- 3 tbsp granulated sugar
- 1 tsp vanilla extract
- 1 packet (2 ¼ tsp) unflavored gelatin
- 3 tbsp cold water
For the ganache topping:
- 6 oz semisweet chocolate, chopped
- ¾ cup heavy cream
- 1 tbsp unsalted butter
Tools You’ll Need
- 9-inch springform pan
- Stand mixer or hand mixer
- Double boiler (or a heatproof bowl over a pot of simmering water)
- Rubber spatula
- Plastic wrap
- Offset spatula (optional, but makes you feel fancy)
Pro Tips
Before you start, a few things I learned the hard way.
1. Use a springform pan, no exceptions. This cake has a soft mousse layer. A regular cake pan will turn unmolding into a disaster.
2. Don’t rush the gelatin. It needs to bloom in cold water for a full 5 minutes before you melt it. Skip this and your mousse won’t set right.
3. Let your chocolate cool slightly before folding it in. Hot chocolate will deflate whipped cream almost instantly. Aim for just-warm, not hot.
4. Chill between every layer. I know it’s tempting to rush. But each layer needs time in the fridge to firm up before the next one goes on.
5. Run a hot knife under water before slicing. Wipe it dry, then cut. Clean slices every time.
Substitutions and Variations
This cake is pretty flexible once you know the base technique.
- Gluten-free: Swap the all-purpose flour for a 1:1 gluten-free baking blend.
- Dairy-free: Use coconut cream instead of heavy cream, and a dairy-free chocolate.
- Espresso boost: Add 1 tsp of espresso powder to the cake batter for a deeper chocolate flavor (you won’t taste coffee, just more chocolate).
- White chocolate version: Swap the mousse and ganache chocolate for white chocolate, but cut the sugar in the mousse since white chocolate is sweeter.
- Single-layer version: Skip the cake base entirely and pour the mousse straight into the springform pan for a crustless mousse cake.
Make Ahead Tips
This cake actually gets better with a day of rest.
- The cake base can be baked up to 2 days ahead, wrapped tightly, and kept at room temperature.
- The full assembled cake (without ganache) can sit in the fridge for up to 3 days.
- Add the ganache topping the day you plan to serve it for the cleanest finish.
How to Make It
Step 1: Bake the cake base. Preheat your oven to 350°F. Grease your springform pan and line the bottom with parchment.
Whisk the flour, sugar, cocoa powder, baking soda, baking powder, and salt together in a large bowl.
Add the egg, buttermilk, oil, and vanilla. Mix until smooth.
Slowly stir in the hot coffee. The batter will turn thin, that’s normal.
Pour into the pan and bake for 30 to 35 minutes, until a toothpick comes out clean.
Let it cool completely in the pan.
Step 2: Bloom the gelatin. Sprinkle the gelatin over the cold water in a small bowl. Let it sit for 5 minutes.
Step 3: Melt the chocolate. Heat ½ cup of the heavy cream in a saucepan until it just starts to simmer.
Pour it over the chopped chocolate and let it sit for 1 minute, then stir until smooth.
Microwave the bloomed gelatin for 10 seconds to liquefy it, then stir it into the warm chocolate mixture.
Let this cool until just warm to the touch.
Step 4: Whip the cream. In a separate bowl, whip the remaining 1 ½ cups of cream with the sugar and vanilla until soft peaks form.
Step 5: Fold it together. Gently fold the cooled chocolate mixture into the whipped cream in two batches. Don’t overmix, you want it to stay light and airy.
Step 6: Assemble. Keep the cooled cake base in the springform pan. Pour the mousse over the top and smooth it with a spatula.
Cover and refrigerate for at least 4 hours, or overnight.
Step 7: Make the ganache. Heat the cream until simmering, then pour over the chopped chocolate. Let sit for a minute, stir until smooth, then stir in the butter.
Let the ganache cool for about 10 minutes, until it’s pourable but not hot.
Step 8: Top and serve. Pour the ganache over the chilled mousse and tilt the pan slightly to spread it evenly.
Chill for another 15 minutes to set the ganache, then release the springform and slice.
Leftovers and Storage
This cake keeps well in the fridge for up to 5 days, covered tightly.
It also freezes surprisingly well. Slice it first, wrap each piece in plastic, then foil, and freeze for up to 2 months.
Thaw slices in the fridge overnight before serving.
Nutritional Notes and Pairings
This is a rich dessert, so small slices go a long way. A standard cut serves 10 to 12 people comfortably.
For pairing, a glass of espresso or a strong black coffee cuts through the richness nicely. If you want something cold, a splash of dark rum on the side works too.
FAQ
Why is my mousse not setting? Most likely the gelatin wasn’t bloomed long enough, or the chocolate mixture was too hot when you folded it into the whipped cream.
Can I make this without gelatin? You can, but the mousse will be softer and less sliceable. It’ll taste the same, just messier to serve.
Can I use milk chocolate instead of semisweet? You can, but reduce the sugar in the mousse since milk chocolate is sweeter.
Why did my cake layer sink in the middle? This usually means it was slightly underbaked or the oven door was opened too early. Check with a toothpick before pulling it out.
Can I make cupcakes instead of one big cake? Yes. Bake the cake base in a lined muffin tin for about 18 minutes, then top each one with mousse and ganache once cooled.
Wrapping Up
This cake takes a little patience, but every layer is simple on its own.
If you make it, I’d love to hear how it turned out. Drop a comment below with your results, or any questions before you start.
