Preheat the oven to 350°F. Grease a 9-inch springform pan and line the bottom with parchment paper.

In a bowl, combine flour, sugar, cocoa powder, baking soda, baking powder, and salt. Mix well.

In another bowl, whisk together milk, vegetable oil, vanilla, egg white, and hot water.

Add dry ingredients to wet ingredients and mix until smooth.

Pour batter into the prepared pan and bake for 12-15 minutes, until a toothpick comes out clean.

Remove cake from oven, let cool, then prepare the cheesecake filling.

In a large bowl, beat cream cheese, sugar, and cocoa powder until smooth.

Add sour cream and vanilla, blending well.

Mix melted chocolate into the cream cheese mixture.

Beat eggs one at a time, then fold in cooled cake layer.

Bake the assembled cheesecake in a water bath at 300°F for 1 hour and 15 minutes.

Turn off oven, leave cheesecake inside for 30 minutes, then cool and refrigerate overnight.

Once cooled, whip heavy cream with cocoa powder, powdered sugar, and vanilla. Pipe onto the cheesecake and garnish with sprinkles if desired.