01 - Line an 8x8 inch baking pan with parchment paper, ensuring there is overhang for easy removal.
02 - In a large mixing bowl, combine the melted butter with 1 cup creamy peanut butter, mixing until smooth.
03 - Stir in the powdered sugar and graham cracker crumbs, then add vanilla extract and mix thoroughly until the mixture forms a thick dough.
04 - Firmly press the peanut butter mixture into the prepared pan, smoothing the surface with a spatula.
05 - Place chocolate chips and 1/4 cup peanut butter in a microwave-safe bowl. Heat in 30-second intervals, stirring after each until fully melted and smooth.
06 - Pour the melted chocolate-peanut butter mixture over the prepared base and spread evenly.
07 - Refrigerate the pan for at least 2 hours, or until the bars are completely set.
08 - Once chilled, lift the slab from the pan using the parchment overhang. Cut into 16 bars and serve.