- 4 ounces cream cheese, softened
- ⅓ cup peanut butter
- ⅛ cup sugar
- 1 egg yolk (save the egg white for the brownie batter)
- 1 tablespoon milk
- ½ cup (1 stick) unsalted butter, melted
- 1 cup sugar
- 1 egg plus 1 egg white
- ½ teaspoon vanilla extract
- ¼ teaspoon salt
- ½ teaspoon baking powder
- ⅓ cup unsweetened cocoa powder
- ⅔ cup flour
Preheat oven to 350 F. Spray an 8-x-8-inch baking pan with cooking spray, then line with foil (or parchment), leaving an overhang on 2 sides to create a sling. Spray the foil with cooking spray.
In the bowl of a stand mixer fitted with the paddle attachment, beat the sugar and cream cheese on medium until combined. Add the peanut butter to the bowl and beat to incorporate fully. Finally, mix in the egg yolk and milk until the cheesecake batter is smooth; set aside.
Combine the cocoa powder, flour, salt, and baking powder in a medium bowl and whisk to combine. In another medium bowl, whisk together the sugar and melted butter. Add the whole egg as well as the egg white and the vanilla extract and whisk to combine. Add the dry ingredients to the wet and use a rubber spatula to mix until combined.
Smooth 2/3 of the brownie batter in the bottom of the prepared baking pan. Add the cheesecake batter on top and smooth to form an even layer. Drop the remaining brownie batter by spoonfuls on top of the cheesecake and then use a knife to swirl the two together.
Bake for 25-30 minutes (probably closer to 35 minutes if you're baking in Pyrex), or until a thin knife inserted in the center comes out with just a few moist crumbs attached. Remove the pan to a cooling rack. Once the brownies have cooled, use the foil sling to lift them out of the pan and then cut them into squares.