Preheat your oven to 325ºF.
Line a 10-inch round baking pan or springform pan with non-stick aluminum foil.
In your stand mixer fitted with the paddle attachment, combine cream cheese, sugar, and vanilla extract.
Add in eggs one at a time, mixing just until incorporated.
Stir in sour cream and melted chocolate until blended.
Pour the batter into the prepared pan.
Bake in the preheated oven for about 45 minutes.
Cool completely in the pan.
Chill the cheesecake in the refrigerator for at least 4 hours.
For the cake layer, heat your oven to 350ºF.
Grease and flour two 10-inch round pans and line the bottoms with parchment.
In a large bowl, stir together sugar, flour, cocoa, baking powder, baking soda, and salt.
Add in eggs, milk, oil, and vanilla; beat on medium speed for 2 minutes.
Stir in boiling water.
Pour the batter into prepared pans.
Bake for 30 to 35 minutes.
Allow the cakes to cool for 10 minutes before removing them from the pans.