In a bowl, beat 1/2 cup butter, peanut butter, powdered sugar and water with an electric mixer until smooth. Spread mixture evenly over brownies (still in pan).
Microwave chocolate chips and 1/4 cup butter for 30-60 seconds; stir until smooth. Cool for 10 minutes, then spread over peanut butter mixture in brownie pan.
Refrigerate until chocolate is set (approximately 30 minutes).