In a medium bowl, stir together the melted butter, pretzel crumbs, powdered sugar and 1 cup of the peanut butter until well-combined. Press the mixture evenly into the bottom of an ungreased 9×13-inch baking dish, then set aside.
Combine the chocolate chips and the remaining 1/4 cup peanut butter in a microwave-safe bowl or measuring cup. Microwave in 30-second intervals, stirring in between, until the chocolate and peanut butter are melted and smooth.
Ensure the mixture is well-combined, then spread over the peanut butter-pretzel layer. Refrigerate for at least 1 hour before cutting into squares. Enjoy!