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 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 firmly into an even layer, smoothing the surface with a spatula.
04 - In a microwave-safe bowl, combine the chocolate chips and remaining 1/4 cup peanut butter. Microwave in 20-second intervals, stirring between each, until completely melted and smooth.
05 - Pour the melted chocolate mixture over the peanut butter base, spreading it into an even layer across the entire surface.
06 - Refrigerate the bars for at least 2 hours, or until the chocolate topping is firm to the touch.
07 - Lift the chilled slab out of the dish using the parchment overhang. Place on a cutting board and slice into 16 even squares.