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 of peanut butter, stirring until smooth. Add the powdered sugar and graham cracker crumbs, mixing thoroughly until a thick, uniform dough forms.
03 - Transfer the mixture to the prepared baking dish and press it evenly across the bottom. Smooth the surface with a spatula to ensure an even layer.
04 - Place the chocolate chips and 1/4 cup of peanut butter in a microwave-safe bowl. Microwave in 20-second intervals, stirring after each burst, until the mixture is completely melted and glossy.
05 - Pour the melted chocolate mixture over the peanut butter base, spreading it into an even layer with a spatula.
06 - Refrigerate the dish for at least 2 hours, or until the chocolate topping is firm to the touch.
07 - Use the parchment overhang to lift the slab out of the dish. Place on a cutting board and slice into 16 even squares.
08 - Keep any remaining bars in an airtight container stored in the refrigerator to maintain freshness and firmness.