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. Stir until smooth and fully blended. Add the sifted 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 firmly into an even layer. Smooth the surface with a spatula.
04 - In a microwave-safe bowl, combine the semisweet chocolate chips and remaining 1/4 cup creamy peanut butter. Microwave in 20-second intervals, stirring between 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 pan 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.