Preheat oven to 350°F. Spray two 8-inch pans with nonstick spray, line with parchment.
Mix flour, cocoa, sugar, baking powder, baking soda, salt in a bowl.
Whisk buttermilk, oil, eggs, vanilla in another bowl.
Create a well, add wet ingredients, mix until smooth, then add hot coffee.
Divide batter evenly into pans, bake 30 minutes until toothpick comes out clean.
Cool completely before removing from pans.
For the compote, boil blackberries, sugar, lemon juice, cinnamon, lemon zest, water.
Cook 5-6 minutes, add cornstarch mixture, cook until thickened. Chill 1 hour.
For frosting, beat cream cheese and butter, sift in sugar, cocoa, salt.
Add vanilla, beat until smooth.
Level cakes, spread frosting on plate, layer cake, pipe dam, add compote.
Top with second cake, frost outside, refrigerate 20 minutes.
Decorate with skulls, blackberries, rose petals.