For the filling: In the bowl of an electric mixer, beat the cream cheese and sugar until well combined. Add the egg, vanilla, and flour until well combined. Set aside.

For the cake: in a large bowl, mix the cocoa, chocolate, and espresso powder. Pour the boiling water into the bowl and cover. Let stand for 5 minutes. In a small bowl, whisk together the flour, salt, and baking soda.Whisk the chocolate mixture until it is smooth. Let cool to room temperature. When it has cooled, whisk in the sour cream.

In the mixing bowl, beat the butter, brown sugar, and vanilla for about 3 minutes, or until light and fluffy. Add the eggs, one at a time, until combined. On low speed gradually add the flour mixture and the melted chocolate mixture alternatively, beginning and ending with the flour, until the batter is smooth.

Pour a little more than half the batter into the prepared pan. Pour the cheesecake filling into the center of the batter, not allowing it to touch the edges of the pan. Pour the remaining batter of the filling. Bake the cake for about 50 minutes, or until a toothpick comes out with moist crumbs. Let cool on a rack for 10 minutes, then turn the cake out and let cool completely.