The cake layer serves as the delicious foundation for the mousse. Here’s how to get it just right:

Preheat your oven to 350°F (175°C). Grease a 9-inch springform pan and line the bottom with parchment paper for easy removal later.

In a large bowl, sift together the all-purpose flour, cocoa powder, baking powder, baking soda, and salt. This step ensures your cake will be light and airy, with no lumps in the batter.

In another bowl, whisk together the sugar, milk, oil, eggs, and vanilla extract. Make sure the mixture is smooth and well combined.

Gradually add the dry ingredients to the wet mixture, mixing gently to combine. The batter will be slightly thin, but that’s perfectly fine.

Stir in the hot coffee—this might seem odd, but it intensifies the chocolate flavor and helps keep the cake moist.

Pour the batter into the prepared pan and bake for 25-30 minutes. To test for doneness, insert a toothpick in the center; it should come out clean.

Once done, let the cake cool in the pan for 10 minutes, then remove it from the pan and transfer to a wire rack to cool completely.

Pro Tip: If your cake rises unevenly, wrap the outside of your pan with a damp towel. It helps create a more even rise for a perfectly flat top.

Now comes the magic—the light, fluffy mousse that makes this cake so special. Here's how to get it smooth and airy:

Melt the dark chocolate and butter in a heatproof bowl using a double boiler or microwave. Stir until smooth and let it cool to room temperature.

In a separate bowl, whisk together the egg yolks and sugar until pale and slightly thickened. Stir in the vanilla extract for an added layer of flavor.

If you're using gelatin, bloom it by sprinkling it over cold water in a small bowl. Let it sit for 5 minutes, then microwave for a few seconds until dissolved. Add it to the melted chocolate mixture.

Fold the egg yolk mixture into the chocolate slowly, making sure everything is well incorporated.

In a chilled mixing bowl, whip the heavy cream until soft peaks form. Then, gently fold the whipped cream into the chocolate mixture in two batches, being careful not to deflate the mousse.

Pro Tip: The key to a light mousse is in the folding technique. Use a spatula and fold in the whipped cream gently, so the mousse stays airy and smooth.

This is where the magic comes together! Here’s how to layer the mousse and cake perfectly:

Place the cooled cake layer back in the springform pan. If your cake has domed, trim the top to create a flat surface.

Pour the mousse over the cake, spreading it evenly with a spatula. Tap the pan gently on the counter to remove any air bubbles.

Refrigerate the cake for at least 4 hours or overnight to allow the mousse to set completely. The longer it sits, the more the flavors will meld together.

Pro Tip: Make sure the mousse has fully set before serving. It should hold its shape when sliced.

The rich dark chocolate ganache is the finishing touch that takes this cake to the next level:

In a small saucepan, heat the heavy cream until it just begins to simmer (don’t let it boil).

Pour the hot cream over the chopped dark chocolate. Let it sit for 1-2 minutes, then stir until smooth and glossy.

Stir in the butter for extra richness and shine.

It’s time to give your cake that professional finish:

Carefully remove the cake from the springform pan and transfer it to a serving plate.

Pour the ganache over the chilled mousse, allowing it to drip down the sides. For a clean finish, use a spatula to smooth out the top.

Chill for another 15-20 minutes to allow the ganache to set before slicing.

Garnish with whipped cream, chocolate shavings, or fresh berries to elevate the presentation.