Preheat the oven to 350 degrees. Line am 8x8 with aluminum foil and lightly spray with cooking spray. Set aside.
To make the Cheesecake Layer: Beat the cream cheese until smooth and creamy for about one minute. Beat in sugar and vanilla until smooth. Lastly beat in the egg until smooth. Set aside.
To make the brownie layer:
Put the chocolate, butter, and oil into a microwave safe bowl. Cook 30 seconds at a time stirring until it is melted and smooth.
In a large bowl whisk together flour, cocoa powder, baking powder, and salt. Set aside.
In a medium bowl add brown sugar, sugar, buttermilk, egg whites, and vanilla. Whisk vigorously until the batter is thick and glossy. Slowly add the melted chocolate mixture and mix until incorporated. Gradually add the flour mixture and stir until incorporated. Reserve 1/2 cup of the brownie mixture.
Pour mixture into the bottom of the prepared pan. Pour the cheesecake mixture on top. Use the reserved 1/2 cup of brownie mixture and drop large dollops on top. Swirl with a knife or the bottom of a wooden spoon.
Bake for 40-45 minutes until the top is just set. Let cool completely and cut into 2 inch squares.