In a large bowl, combine the graham crackers, powdered sugar, and peanut butter. Add the melted butter and mix well. Add up to 1/2 cup more powdered sugar if mixture is too wet. You want it to come together without drying it out. Spread mixture in the bottom of an ungreased 9x13-inch pan.

Microwave chocolate chips and peanut butter for 30 seconds. Stir and continue microwaving in 15 second bursts until melted, stirring frequently. Alternately melt with a double broiler. Pour melted chocolate over the peanut butter layer and spread evenly with a spatula. Refrigerate for 30 minutes or freeze for 15 minutes, until chocolate is just barely set. Cut squares. Keep refrigerated.