Preheat your oven to 350°F (175°C) and prepare two 8-inch round cake pans with nonstick spray and parchment paper.

In a large bowl, sift together flour, black cocoa powder, sugar, baking powder, baking soda, and salt.

In another bowl, whisk together buttermilk, oil, eggs, and vanilla until smooth.

Combine wet and dry mixtures, then gradually add hot coffee mixing until smooth.

Divide batter between pans and bake for 30-33 minutes, checking with a toothpick.

For the compote, heat blackberries, sugar, lemon juice, zest, and cinnamon in a saucepan. Once boiling, add cornstarch mixed with water and cook until thick.

Cool cakes in pans for 10 minutes before transferring to wire racks to cool completely.

Beat cream cheese and butter until creamy, then mix in sifted powdered sugar and black cocoa.

Level the tops of the cake layers, spread a thin layer of frosting, and fill with blackberry compote.

Add the second cake layer, crumb coat with frosting, and chill for 20 minutes.

Frost the top and sides with remaining frosting, decorating with chocolate skulls, blackberries, and rose petals.