Preheat the oven to 350°F. Prepare a 9-inch springform pan and an 8-inch round cake pan by lining them with parchment paper and spraying with non-stick spray.

Whisk together the flour, cocoa powder, and salt in a mixing bowl.

Cream the butter and granulated sugar together until fluffy and light in color. Add in the sour cream, vegetable oil, vanilla extract, eggs, and red food coloring, mixing until fully incorporated.

Combine the dry ingredients with the wet ingredients, alternating with buttermilk. Mix in the baking soda and vinegar until just combined.

Divide the batter evenly between the prepared pans. Bake the cake layers for 18-20 minutes until they spring back lightly when touched. Cool them fully.

Prepare your cheesecake filling by crushing the Oreos into fine crumbs. In a separate bowl, beat the cream cheese until smooth, then mix in the Oreo crumbs, sugar, cornstarch, sour cream, vanilla, and eggs until creamy.

Fold in the remaining crushed Oreos into the cheesecake mixture. Carefully pour this over the cooled red velvet layers in the springform pan.

Bake the cheesecake in a water bath at 300°F for 90 minutes. Turn off the oven and let the cheesecake cool gradually inside to avoid cracks, then refrigerate overnight.

Make the ganache by microwaving the heavy cream and dark chocolate chips until melted and smooth. Pour this over the cheesecake.

Decorate with crumbled red velvet cake and dollops of cream cheese frosting just before serving.