In a large microwave safe bowl melt the butter on high power in 30 second increments (stir between heat cycles). Add powdered sugar, graham cracker crumbs, and peanut butter to the bowl and mix well.
Spread the peanut butter mixture into a foil or parchment lined 8x8 baking dish (make sure to leave some of the foil or parchment overhanging so it's easy to remove the bars).
In another microwave safe bowl melt the chocolate chips on high power in 30 second intervals (stirring between heat cycles) until melted and smooth. Spread melted chocolate evenly on top of the peanut butter bars.
Refrigerate the bars until firm (about 1 hour). Lift the bars from the pan and use a warm knife to slice into 16 evenly sized bars.
Notes
Calories are automatically generated. For best results calculate based on your exact ingredients.