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 the melted butter and 1 cup creamy peanut butter, stirring until smooth. Add the powdered sugar and graham cracker crumbs, mixing until a thick, uniform dough forms.
03 - Transfer the dough to the prepared baking dish and press it evenly across the bottom. Use a spatula to smooth the surface.
04 - In a microwave-safe bowl, combine the chocolate chips and 1/4 cup creamy peanut butter. Microwave in 20-second intervals, stirring between each, until completely melted and smooth.
05 - Pour the melted chocolate mixture over the peanut butter base, spreading it into an even layer with a spatula.
06 - Refrigerate the pan for at least 2 hours, or until the chocolate topping is set and firm to the touch.
07 - Lift the slab out of the dish using the parchment overhang. Cut into 16 even squares and serve.
08 - Keep any remaining bars in an airtight container stored in the refrigerator.