01 - Line a 9x9-inch baking dish with parchment paper, leaving an overhang on two sides for easy removal.
02 - In a medium bowl, whisk together the melted butter and 1 cup of peanut butter until smooth. Add the powdered sugar and graham cracker crumbs, then stir until a thick, uniform dough forms.
03 - Transfer the dough to the prepared baking dish and press it firmly into an even layer using a spatula. Smooth the surface so it is level.
04 - Combine the chocolate chips and remaining 1/4 cup of peanut butter in a microwave-safe bowl. Microwave in 20-second intervals, stirring after each burst, until fully melted and glossy.
05 - Pour the melted chocolate mixture over the peanut butter base and spread it into an even layer using a spatula.
06 - Refrigerate the pan for at least 2 hours, or until the chocolate topping is firm to the touch.
07 - Lift the slab out of the dish using the parchment overhang. Place on a cutting board and slice into 16 even squares.
08 - Keep any remaining bars in an airtight container stored in the refrigerator.