01 - Line an 8x8 inch baking pan with parchment paper, allowing excess to hang over the sides for easy removal.
02 - In a large bowl, combine melted unsalted butter and 1 cup creamy peanut butter until mixture is smooth.
03 - Mix in powdered sugar and graham cracker crumbs, then add vanilla extract. Stir until a thick, homogeneous dough forms.
04 - Press the peanut butter mixture evenly into the prepared pan and smooth the surface with a spatula.
05 - In a microwave-safe bowl, melt semi-sweet chocolate chips with 1/4 cup creamy peanut butter using 30-second intervals, stirring well after each, until completely melted and glossy.
06 - Pour the melted chocolate-peanut butter mixture over the base and distribute evenly with a spatula.
07 - Refrigerate for at least 2 hours, or until the bars are fully set and firm to touch.
08 - Lift the bars from the pan using the parchment paper overhang, cut into 16 even squares, and serve.