Preheat oven to 350 degrees F.
Lightly grease a 9x9 baking pan.
Brownies: combine flour, cocoa, salt, baking powder, and sugar, stir to combine.
In separate bowl combine eggs, vanilla, and melted butter, add into dry ingredients.
Stir to combine, stirring until smooth.
Add in chocolate chips.
Pour batter into greased baking pan.
Peanut Butter Layer: combine peanut butter, butter, sugar, flour, egg, and vanilla.
Mix with a hand mixer until fluffy.
Drop tablepoons of the peanut butter mixture over brownie batter, smooth out over top.
Bake at 350 degrees for 30 minutes.
Allow to cool completely.
Icing: Combine butter, cocoa, sugar, and 1 tablespoon of milk.
Mix with a hand mixer until smooth, adding in additional milk as needed.
Stir in vanilla and peanut butter.
Spread icing over cooled brownies.
Chill 15-20 minutes before cutting.