Preheat the oven to 175 degrees Celsius or 350 degrees Fahrenheit. Grease a round cake pan and line the bottom with parchment.

In a large bowl, whisk together the flour, cocoa powder, sugar, baking soda, baking powder, and salt.

Create a well in the center. Add the eggs, milk, vegetable oil, and vanilla. Mix with a hand whisk or electric mixer until the batter just comes together.

Pour in the hot coffee slowly while mixing. The batter will be thin. That is exactly right. The thin batter yields a moist, dense, yet tender crumb.

Pour into the prepared pan. Bake for 25 to 30 minutes. A toothpick inserted into the center should come out with a few moist crumbs, not wet batter.

Let the chocolate cake cool in the pan for about ten minutes. Then transfer to a wire rack to cool completely. Cooling completely is essential. If the cake is even slightly warm, the mousse will melt on contact.

In a medium bowl, beat the cream cheese, powdered sugar, and vanilla until completely smooth and free of lumps.

In a tiny bowl, sprinkle the gelatin over two tablespoons of cold water. Let it sit for two to three minutes until it absorbs the water and thickens. This is called blooming.

Gently melt the bloomed gelatin in the microwave for five to ten seconds, or over a double boiler. Do not boil it. Once liquid, add a spoonful of the cream cheese mixture into the gelatin and stir. Then add the gelatin mixture back into the cream cheese bowl. This prevents small gelatin strands from forming. Fold until smooth.

In a separate bowl, whip the heavy cream until soft to medium peaks form. It should be fluffy and hold shape, but not so stiff that it becomes grainy.

Fold the whipped cream into the cream cheese mixture gradually. Use a large spoon or silicone spatula. Cut through the center, turn the bowl, and fold gently. This keeps the mousse light and airy.

Place the cooled chocolate cake into a lined springform pan or a ring once set. Spread the vanilla mousse over the cake layer evenly. Smooth the top with an offset spatula.

Refrigerate for a minimum of four hours. Overnight is better if you have the time. The mousse must fully set before ganache is added.

Chop the chocolate into small uniform pieces and put it in a heatproof bowl.

Heat the cream until it is steaming, then begins to simmer around the edges. Do not boil it. Pour the cream over the chocolate. Let it sit for one minute.

Add the butter. Stir from the center, going gradually in circular motions. The mixture will turn into a shiny, silky ganache.

Allow ganache to cool slightly for five minutes. If it is too hot, it will melt the mousse. If it is too cold, it will become stiff and hard to spread.

Pour the ganache over the chilled cake. Start from the centre and let it flow over the edges. Use a small spatula to gently spread it if needed.

Decorate with chocolate shavings and extra melted chocolate swirls. Use a chilled bowl or a chilled bar of chocolate and a vegetable peeler to create shavings and curls.

For chocolate swirls, pour a small amount of melted chocolate into a small piping bag or zip top bag, cut a tiny corner, and pipe stripes, zig zags, or swirls on parchment. Let them set, then arrange them on the cake.

Serve sliced chilled. Use a hot knife for the cleanest cuts. Dip the blade in hot water, wipe dry, and slice.