01 - Line a 9x9-inch baking dish with parchment paper, leaving an overhang on the sides for easy removal.
02 - In a medium bowl, combine melted butter and 1 cup peanut butter until smooth. Add powdered sugar and graham cracker crumbs; stir until well mixed and a thick dough forms.
03 - Press the mixture evenly into the prepared baking dish, smoothing the top with a spatula.
04 - In a microwave-safe bowl, combine chocolate chips and 1/4 cup peanut butter. Microwave in 20-second intervals, stirring after each, until melted and smooth.
05 - Pour the chocolate mixture over the peanut butter layer, spreading evenly to the edges.
06 - Refrigerate for at least 2 hours or until the chocolate layer is completely firm.
07 - Lift the bars out of the pan using the parchment overhang. Cut into 16 even squares.
08 - Store leftovers in the refrigerator in an airtight container.