Preheat oven to 350°. Coat a 9-inch square baking pan lightly with cooking spray.
Combine flour, sugar, baking powder, and salt. Set aside.
In a separate bowl, combine peanut butter, melted butter, milk, vanilla extract, and eggs. Stir well.
Add peanut butter mixture to flour mixture, stirring until combined. Stir in chocolate chips.
Transfer batter into baking pan. Arrange the peanut butter cups over the batter.
Bake for 19 minutes, or until a wooden pick inserted into the center comes out with moist crumbs. Cool in pan on wire rack.