Preheat the oven to 350°F (175°C).
Grease and line two 9-inch round cake pans.
Whisk together the flour, sugar, black cocoa, cocoa powder, baking powder, baking soda, and salt.
In another bowl, whisk the eggs, buttermilk, oil, melted butter, vanilla, and vinegar.
Gradually mix the wet ingredients into the dry ingredients.
Slowly stir in the hot coffee until the batter is smooth.
Divide the batter evenly between the prepared pans.
Bake for 30–35 minutes or until a toothpick comes out clean.
Cool the cakes in the pans for 10 minutes.
Transfer the cakes to a wire rack and cool completely.
Beat the cream cheese and butter until smooth.
Gradually beat in the powdered sugar.
Mix in the vanilla extract until fluffy.
Frost the cooled cake layers evenly.
Decorate with chocolate shavings or black cocoa crumbs if desired.