Line a 9x9 inch baking pan with parchment paper, leaving an overhang on two sides for easy removal.

In a large mixing bowl, stir together the graham cracker crumbs, powdered sugar, melted butter, and 1 cup of the creamy peanut butter until the mixture is well combined.

Press the crumb mixture firmly and evenly into the bottom of the prepared baking pan using a spatula or the bottom of a measuring cup.

In a microwave-safe bowl, combine the chocolate chips and the remaining 1/2 cup of creamy peanut butter.

Heat the chocolate mixture in 30-second increments, stirring thoroughly after each interval, until the chocolate is completely melted and smooth.

Pour the chocolate mixture over the peanut butter base and spread it into an even layer with an offset spatula.

Refrigerate the pan for at least 2 hours, or until the chocolate topping is firm and the base is fully set.

Lift the bars from the pan using the parchment paper overhang and slice into 16 uniform squares using a sharp knife.