Whisk the flour, cocoa, sugar, baking powder, baking soda, and salt. Mix the eggs, buttermilk, oil, and vanilla separately, then combine with the dry ingredients. Gradually add the hot coffee or water.

Divide the batter between the cake pans and bake for 28–33 minutes. Cool completely.

Beat the cream cheese until smooth. Add the sugar, sour cream, orange zest, orange juice, and vanilla. Mix in the eggs one at a time, then add the flour.

Pour into the springform pan and bake at 325°F (160°C) for 50–65 minutes, until the edges are set and the center has a slight wobble. Cool gradually, then refrigerate for 4–6 hours or overnight.

Heat the cream until steaming, pour it over the chopped chocolate, and let it stand for 3 minutes. Stir until smooth and add the optional butter. Cool until spreadable.

Stack the first chocolate sponge, a thin layer of ganache, the chilled cheesecake, and the second sponge.

Apply a crumb coat, chill, then spread the remaining ganache over the cake.