Preheat your oven to 350°F (175°C) and grease a 9×13 inch baking pan.

In a large mixing bowl, combine the melted butter, granulated sugar, and brown sugar until smooth.

Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.

In a separate bowl, whisk together the flour and cocoa powder, then fold into the butter mixture until combined.

Pour half of the brownie batter into the prepared pan, spreading it evenly.

In another bowl, blend together peanut butter, cream cheese, and powdered sugar until smooth.

Spread the peanut butter mixture over the brownie layer.

Spoon the remaining brownie batter over the peanut butter layer and swirl with a knife.

Bake for 30-35 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.

Allow to cool before cutting into squares.