In a saucepan, melt butter over medium heat. Remove from heat and stir in graham cracker crumbs, powdered sugar, and peanut butter until well combined.

Press the peanut butter mixture evenly into a greased 9x13 inch baking dish. Chill in the refrigerator for 10 minutes.

In a microwave-safe bowl, melt chocolate chips until smooth, stirring every 30 seconds. Spread over the chilled peanut butter layer.

Refrigerate until the chocolate is set, about 5 minutes. Cut into bars and serve.