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 and 1 cup peanut butter until smooth.
03 - Mix in powdered sugar and graham cracker crumbs, then add vanilla extract. Stir thoroughly until a thick, uniform dough forms.
04 - Evenly press the peanut butter mixture into the prepared pan, smoothing the surface with a spatula.
05 - Melt chocolate chips and 1/4 cup peanut butter together in a microwave-safe bowl using 30-second intervals, stirring after each session, until fully melted and silky.
06 - Pour the chocolate-peanut butter mixture over the base and spread it evenly over the surface.
07 - Refrigerate for at least 2 hours or until completely firm.
08 - Lift the bar slab from the pan using the parchment overhang, cut into 16 bars, and serve.