Line a 13 by 9 by 2-inch pan with foil.
Combine the butter, peanut butter, sugar, and graham cracker crumbs in a food processor. Process until the mixture forms a ball. Press into the foil-lined pan using your hands or a spatula.
Melt the chocolate chips in a double boiler over simmering water or in a microwave-safe glass dish in the microwave for 1 minute on high. Stir. If the chocolate has not completely melted, microwave for 10 seconds more, then stir. Spread evenly over the cookie layer with a spatula. Chill for several hours.
When ready to serve, allow the candy to come to room temperature before cutting into pieces. Store in an airtight container in the refrigerator.