01 - Line an 8x8 inch baking pan with parchment paper, leaving an overhang for easy lifting.
02 - In a large mixing bowl, blend melted butter with 1 cup creamy peanut butter until smooth.
03 - Stir powdered sugar and graham cracker crumbs into the peanut butter mixture, followed by the vanilla extract. Mix until a dense, uniform dough forms.
04 - Firmly press the peanut butter mixture evenly into the prepared pan, smoothing the surface with a spatula.
05 - In a microwave-safe bowl, combine semi-sweet chocolate chips and 1/4 cup creamy peanut butter. Microwave in 30-second intervals, stirring after each, until fully melted and glossy.
06 - Spread the melted chocolate-peanut butter topping evenly over the base layer.
07 - Refrigerate the assembled bars for at least 2 hours or until the topping is set and firm.
08 - Once thoroughly chilled, lift the bars out of the pan using the parchment overhang. Cut evenly into 16 bars and serve.