Preheat the Oven: Start by preheating your oven to 325°F (163°C). Line the bottom of a 9-inch springform pan with parchment paper and lightly grease the sides.

Make the Cheesecake Batter: In a mixing bowl, beat the softened cream cheese until smooth and creamy. Gradually add the sugar and continue beating until well combined.

Add the eggs, one at a time, mixing on low speed until fully incorporated. Stir in the vanilla extract and sour cream until smooth.

Bake the Cheesecake: Pour the cheesecake batter into the prepared pan. Place the pan on a baking sheet and bake for 45-50 minutes, or until the center is set but still slightly jiggly. Allow the cheesecake to cool completely before proceeding.

Preheat the Oven: Once the cheesecake is baked, increase the oven temperature to 350°F (177°C).

Mix the Dry Ingredients: In a large bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt.

Mix the Wet Ingredients: In another bowl, combine the buttermilk, vegetable oil, egg, and vanilla extract. Gradually add the wet ingredients to the dry ingredients, mixing until just combined. Carefully stir in the boiling water until the batter is smooth.

Bake the Chocolate Cake: Pour the chocolate cake batter over the cooled cheesecake layer in the springform pan. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Allow the cake to cool completely in the pan.

Heat the Cream: In a small saucepan, heat the heavy cream over medium heat until it begins to simmer. Remove from heat and pour over the chocolate chips in a bowl.

Make the Ganache: Let the chocolate and cream sit for a minute, then stir until the chocolate is completely melted and smooth. Stir in the vanilla extract.

Top the Cake: Pour the ganache over the cooled chocolate cake, spreading it evenly with a spatula. Let the ganache set before serving.