01 - Line an 8x8-inch baking pan with parchment paper, allowing excess paper to hang over the sides for easy removal.
02 - In a large mixing bowl, blend melted butter and 1 cup creamy peanut butter until fully smooth.
03 - Add powdered sugar and graham cracker crumbs to the bowl, then stir in vanilla extract. Mix until a thick, homogenous dough forms.
04 - Transfer the peanut butter mixture into the pan and press evenly across the bottom, smoothing the surface with a spatula.
05 - In a microwave-safe bowl, combine chocolate chips and 1/4 cup creamy peanut butter. Microwave in 30-second intervals, stirring in between, until the mixture is fully melted and smooth.
06 - Pour the melted chocolate-peanut butter mixture over the base and spread into an even layer using a spatula.
07 - Refrigerate uncovered for a minimum of 2 hours until the entire slab is set and firm.
08 - Remove from the pan using the overhanging parchment, slice into 16 bars, and serve chilled.