01 - Line an 8x8 inch baking pan with parchment paper, leaving overhang to assist with removal.
02 - In a large bowl, blend melted butter with 1 cup peanut butter until uniformly smooth.
03 - Stir in powdered sugar and graham cracker crumbs, followed by vanilla extract. Mix thoroughly until a dense, cohesive dough forms.
04 - Press the mixture evenly into the prepared pan, smoothing the surface with a spatula.
05 - In a microwave-safe bowl, melt chocolate chips with 1/4 cup peanut butter in 30-second intervals, stirring between each session until the mixture is fully melted and smooth.
06 - Pour the melted chocolate-peanut butter topping over the base and spread into an even layer.
07 - Place pan in the refrigerator for a minimum of 2 hours, allowing bars to set completely.
08 - Once firm, lift bars from the pan using parchment paper. Cut into 16 even bars and serve.