Preheat your oven to 350 degrees Fahrenheit. Grease 3 6-inch cake pans with non-stick spray, line the bottoms with parchment paper rounds, and set them aside.

In a medium bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt. Set aside.

In a large mixing bowl, cream together the butter and granulated sugar until fluffy. Add eggs and vanilla, mixing until smooth.

Gradually add the dry ingredients and buttermilk to the butter mixture, alternating between them, and mixing until smooth. Stir in the hot coffee.

Divide the batter evenly among the prepared cake pans and bake for 39-44 minutes, or until a toothpick inserted into the center comes out clean. Let the cakes cool in the pans for 5 minutes, then transfer them to a wire rack to cool completely.

In a large bowl, whip the softened butter until pale and fluffy. Mix in the melted chocolate until combined.

Sift in the cocoa powder and powdered sugar, then gradually add the heavy cream until the frosting is light and fluffy.

Level the cooled cake layers by removing the domed tops.

Apply a thin layer of buttercream between each layer of cake to create a crumb coat. Chill the cake for 30 minutes.

Apply a final layer of buttercream to the chilled cake and smooth it out.

Make the chocolate ganache by heating cream until steaming, then pouring it over chopped chocolate. Stir until smooth and let it cool slightly.

Pour the ganache over the chilled cake, allowing it to drip down the sides. Chill the cake until the ganache sets.

Pipe decorative swirls of buttercream on top of the cake and garnish with chocolate pieces or shavings.