Line a 7x11 inch rectangular pan or 9x9 inch square pan with parchement paper and set aside.
In a large bowl, mix the graham crackers, sugar, peanut butter and butter until combined.
Pour peanut butter mixture into the prepared baking dish and press down until evenly distributed and flattened across the top.
Melt the chocolate chips in a microwave or on the stove top in a double boiler. Stir until smooth.
Spread chocolate over peanut butter layer.
Chill in refrigerator until firm, at least 2 hours. Allow to sit room temperature for 10 minutes before cutting into squares. Serve chilled.
Leftover bars can be stored in a airtight container in the refrigerator for up to a week or in the freezer for 2-3 months.