Grease an 8x8-inch baking dish and line it with parchment paper.

In a large bowl, stir together the graham cracker crumbs and powdered sugar. Add the melted butter and 1 cup peanut butter and mix until well combined.

Use your hands to evenly press the peanut butter mixture into the prepared pan.

In a medium microwave-safe bowl, combine the chocolate chips and the remaining 2 tablespoons peanut butter. Microwave on high, stirring every 20 seconds, until the mixture is smooth. Evenly spread over the peanut butter layer.

Refrigerate the bars overnight, or until the chocolate is firm and the peanut butter layer is fully set. The chocolate will set up sooner, but the peanut butter layer requires a full overnight chill. Slice and serve.