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. Add the sifted powdered sugar and graham cracker crumbs, then mix thoroughly until a thick, uniform dough forms.
03 - Transfer the dough into the prepared baking dish. Press it evenly across the bottom, using a spatula to smooth the surface.
04 - In a microwave-safe bowl, combine the semisweet chocolate chips with the remaining 1/4 cup of creamy peanut butter. Microwave in 20-second intervals, stirring between each burst, until the mixture is completely melted and silky smooth.
05 - Pour the melted chocolate mixture over the peanut butter base, spreading it into an even layer with a spatula.
06 - Refrigerate the bars for at least 2 hours, or until the chocolate topping is firm to the touch.
07 - Lift the entire 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 to maintain freshness and firmness.