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 creamy peanut butter. Stir until smooth and fully blended.
03 - Add the sifted powdered sugar and graham cracker crumbs to the peanut butter mixture. Stir until well combined and a thick, uniform dough forms.
04 - Transfer the dough to the prepared baking dish. Press it evenly across the bottom and smooth the surface with a spatula.
05 - In a microwave-safe bowl, combine the semisweet chocolate chips with the remaining 1/4 cup of peanut butter. Microwave in 20-second intervals, stirring after each burst, until completely melted and smooth.
06 - Pour the melted chocolate mixture over the peanut butter base, spreading it into an even layer with a spatula.
07 - Refrigerate the bars for at least 2 hours, or until the chocolate topping is firm to the touch.
08 - Lift the entire slab out of the dish using the parchment overhang. Place on a cutting board and slice into 16 even squares. Store any leftovers in an airtight container in the refrigerator.