Line a 13×9 pan with parchment paper and spray with a baking spray.
Preheat oven to 350 degrees.
Cream the butter with sugar in mixing bowl with paddle attachment.
Mix in egg until combined.
Stir in milk and vanilla.
Mix in the flour, baking powder, baking soda and salt.
Stir in bananas, 1/2 cup peanut butter and ¾ cup chocolate chips.
Spread batter in pan, place remaining chocolate chips on top, and the remaining 1/4 cup peanut butter and swirl it in with a toothpick or knife.
Bake for 30-35 minutes or until toothpick comes out clean.