Preheat oven to 325°F and prepare a 9-inch springform pan with parchment and grease.
Beat cream cheese and sugar until smooth, then add eggs one at a time, mixing gently.
Stir in vanilla extract and sour cream until creamy; pour into pan and bake for 40–45 minutes until slightly jiggly.
Cool cheesecake completely then refrigerate for at least 3 hours or overnight.
Preheat oven to 350°F and grease and line two 9-inch cake pans.
Whisk together flour, cocoa powder, sugar, baking soda, baking powder, and salt.
Add eggs, buttermilk, oil, and vanilla extract to dry ingredients and mix until just combined.
Slowly stir in hot coffee; divide batter between pans and bake 30–35 minutes until a toothpick comes out clean.
Cool cake layers completely before assembling.
Heat heavy cream until steaming, pour over chocolate chips, let sit 2 minutes, then stir until smooth and glossy.
Cool ganache until thickened but still spreadable.
Beat butter until creamy, then gradually add powdered sugar, cocoa powder, heavy cream, vanilla extract, and salt; beat until fluffy.
Assemble cake: place one chocolate cake layer on serving plate, spread a thin layer of ganache.
Place chilled cheesecake layer on top, then the second chocolate cake layer.
Frost entire cake with chocolate frosting and smooth the sides.
Pipe decorative chocolate borders on edges and chill cake for 30 minutes before slicing.