In a medium bowl, stir together the graham cracker crumbs, confectioners' sugar, peanut butter, and melted butter until fully combined.

Press the mixture evenly into the bottom of a 9×9-inch ungreased baking dish. Transfer to the refrigerator to chill while you prepare the topping.

In a microwave-safe bowl, combine the chocolate chips and peanut butter. Microwave in 15-second intervals, stirring after each, until smooth and fully melted.

Pour the chocolate mixture over the graham cracker base and spread evenly.

Refrigerate for at least 1 hour, or until set.

Once set, slice into bars and serve chilled or at room temperature.