Chocolate Cheesecake Cake

INGREDIENTS

CHOCOLATE CHEESECAKE:

5 oz

bittersweet chocolate (70% cocoa), chopped

2 8 ounce packages

cream cheese, at room temperature

1/2 cup

+ 3 tablespoons granulated white sugar

2 tbsp

unsweetened cocoa powder

large eggs

CHOCOLATE CAKE:

1 3/4 cups

all-purpose flour

1 1/2 cups

granulated white sugar

2/3 cup

unsweetened cocoa powder (not Dutch process)

1 1/2 tsp

baking soda

1/2 tsp

baking powder

1/2 tsp

salt

1 tsp

instant espresso powder

large eggs, at room temperature

1 1/4 cups

buttermilk, divided

3/4 cup

unsalted butter, at room temperature

1 tsp

vanilla extract

CHOCOLATE SOUR CREAM FROSTING:

2 cups

semisweet chocolate chips

1/2 cup

unsalted butter, at room temperature

1 cup

sour cream

2 tbsp

light (white or golden) corn syrup