Chocolate cake

1. Preheat oven to 329°F / 165°C and prepare 3 round cake pans of 6 inches / 15 cm diameter with parchment paper only in the bottom of the pan.
2. In a bowl, mix and sift together all the dry ingredients, flour, unsweetened cocoa powder, salt, baking powder and baking soda.
3. In another large mixing bowl place the eggs with the sugar, vanilla and vegetable oil and mix with an electric mixer for about 2 minutes until smooth.
4. Then add the buttermilk and coffee and mix again with a mixer to incorporate them.
5. Finish by adding the dry ingredient mixture in batches and mix after each addition with a spatula or whisk until the batter is smooth.
6. Divide the batter into 3 and distribute it into the prepared cake pans.
7. Bake the cakes in the oven at half height for about 35-40 minutes until they are completely baked.
8. Check for baking by plunging a knife blade or toothpick into the center of the cake, it should come out clean or with crumbs, if you still have liquid batter, extend the baking time by 5 minutes.
9. Let the cakes cool a little in their molds before turning them out carefully and leaving them upside down on a rack until they are completely cool.
10. Cover with plastic wrap and place in the refrigerator for at least 2 hours before assembling.

Chocolate Ganache

1. Chop the chocolate with a knife and place in a large container with the cocoa powder.
2. Bring half of the heavy cream to a boil in a saucepan and remove from heat at the first boil.
3. Pour the hot cream all at once over the chocolate and cocoa and let it stand for a few moments before mixing with a spatula until you have a smooth ganache without lumps.
4. Add the other half of the cold heavy cream and mix again to incorporate it.
5. Mix the ganache with a hand blender to smooth it, then cover with plastic wrap and place in the refrigerator for at least 6 hours.

Assembly 

1. Cut out the bumps of the chocolate cakes with a cake leveler.
2. Take out the cooled chocolate ganache and mix it with an electric mixer at medium-low speed until you have a thick, firm and smooth ganache.
3. Place a first sponge cake on a cake board, placed on a cake turntable.
4. Add a layer of chocolate ganache on top of the cake layer and spread it with an angled spatula.
5. Cover with the second layer of chocolate cake and apply another layer of chocolate ganache and smooth it with the spatula.
6. Finish with the last layer of chocolate cake and cover the entire cake with a thin layer of ganache.
7. Immediately apply another layer of ganache, this time thicker, over the entire cake.
8. Decorate with sprinkles or chocolate shavings and place in the fridge for one hour before serving.