01 - Line an 8x8 inch baking pan with parchment paper, ensuring an overhang for easy lifting.
02 - In a large bowl, combine melted butter with 1 cup creamy peanut butter until the mixture is smooth.
03 - Stir in powdered sugar and graham cracker crumbs, then add vanilla extract. Mix thoroughly to form a thick, uniform dough.
04 - Press the peanut butter mixture firmly into the prepared pan, smoothing the surface with a spatula.
05 - In a microwave-safe bowl, melt semi-sweet chocolate chips with 1/4 cup peanut butter in 30-second intervals, stirring between each, until fully smooth.
06 - Pour the chocolate-peanut butter mixture evenly over the base layer and spread to the edges.
07 - Refrigerate the assembled bars for a minimum of 2 hours, or until the topping is fully set.
08 - Lift out the chilled slab using parchment overhang, slice into 16 bars, and serve immediately.