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 - Add the graham cracker crumbs and powdered sugar to the peanut butter mixture. Stir thoroughly until all ingredients are uniformly combined and no dry pockets remain.
04 - Transfer the mixture to the prepared baking dish and press it firmly into an even, flat layer using a spatula or your hands.
05 - Place the semi-sweet chocolate chips and creamy peanut butter in a microwave-safe bowl. Microwave in 30-second intervals, stirring after each interval, until the mixture is completely melted and smooth.
06 - Pour the melted chocolate topping over the peanut butter base and spread it into an even layer using a spatula.
07 - Refrigerate the pan for at least 2 hours, or until the chocolate topping is fully set and firm to the touch.
08 - Lift the entire slab out of the pan using the parchment paper overhang. Place on a cutting board and cut into 16 even bars. Serve chilled or at room temperature.