Chocolate cake

1. Preheat oven to 329°F (165°C) and prepare three 6-inch / 15 cm round cake pans, lined with parchment paper on the bottom only.
2. In a bowl, sift together the flour, cocoa powder, baking powder, baking soda, and salt.
3. In another large bowl, beat the eggs with the sugar, vanilla, and vegetable oil for about 2 minutes until smooth.
4. Add the buttermilk and hot coffee, then mix again until combined.
5. Add the dry ingredients in batches, mixing gently after each addition until the batter is smooth.
6. Divide the batter evenly between the prepared pans.
7. Bake for 35–40 minutes, until a toothpick inserted in the center comes out clean or with a few crumbs.
8. Let the cakes cool slightly, then unmold and cool completely upside down on a rack.
9. Wrap the layers in plastic wrap and chill for at least 2 hours before assembling.

Chocolate ganache

1. Finely chop the chocolate and place it in a large bowl.
2. Heat half of the heavy cream until just simmering, then pour it all at once over the chocolate.
3. Let sit for a few seconds, then stir until smooth.
4. Add the remaining cold heavy cream and mix to combine.
5. Blend briefly with an immersion blender to smooth the ganache.
6. Cover with plastic wrap (touching the surface) and refrigerate for at least 6 hours.

Assembly

1. Level the cooled cake layers.
2. Whip the cold ganache on medium-low speed until thick, smooth, and spreadable.
3. Place the first cake layer on a cake board and turntable.
4. Spread a layer of ganache, add the second cake layer, and repeat.
5. Finish with the last layer and cover the entire cake with a thin crumb coat, then a thicker final layer.
6. Decorate with sprinkles or chocolate shavings and chill for 1 hour before serving.