01 - Line a 9x13-inch baking dish with parchment paper, leaving enough overhang on the sides to lift the bars out later.
02 - In a large mixing bowl, combine the creamy peanut butter and melted unsalted butter. Stir until completely smooth and well blended.
03 - Fold in the graham cracker crumbs and powdered sugar. Stir until the mixture is fully combined and uniform in texture.
04 - Transfer the mixture to the prepared baking dish. Press it down evenly using a spatula or your hands to create a firm, flat layer.
05 - In a microwave-safe bowl, combine the semi-sweet chocolate chips and creamy peanut butter. Microwave in 30-second intervals, stirring after each burst, until fully melted and silky smooth.
06 - Pour the melted chocolate mixture over the peanut butter base. Use a spatula to spread it into an even, smooth layer covering the entire surface.
07 - Refrigerate the bars for at least 2 hours, or until the chocolate topping is completely firm to the touch.
08 - Lift the slab out of the dish using the parchment paper overhang. Place on a cutting board and slice into 16 even bars. Serve chilled.