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, stir together the creamy peanut butter and melted unsalted butter until completely smooth and well blended.
03 - Add the graham cracker crumbs and powdered sugar to the peanut butter mixture. Stir vigorously until all ingredients are fully incorporated and the mixture is uniform in texture.
04 - Transfer the mixture into the prepared baking dish and press it down firmly and evenly using a spatula or your hands to create a flat, compact layer.
05 - Place the semi-sweet chocolate chips and creamy peanut butter in a microwave-safe bowl. Microwave in 30-second intervals, stirring thoroughly after each burst, until the mixture is completely melted and silky smooth.
06 - Pour the melted chocolate mixture over the peanut butter base and spread it into an even layer using a spatula, ensuring full coverage to the edges.
07 - Refrigerate the bars for at least 2 hours, or until the chocolate topping is firm and set completely.
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 or at room temperature.