Prepare your 9×13 inch pan by lining it with parchment paper or lightly greasing it if you prefer. Set aside.
In a medium bowl, pour in 1 cup melted butter. Add 2 cups finely ground graham cracker crumbs and 2 cups confectioners’ sugar.
Add 1 cup creamy peanut butter to the bowl. Mix until everything is evenly combined and holds together when pressed.
Transfer the mixture into the bottom of the pan. Press the layer firmly and evenly into the pan.
In a microwave-safe bowl, combine 1.5 cups milk chocolate chips and the reserved 4 tablespoons peanut butter. Microwave in 30-second intervals, stirring until melted and smooth.
Pour the chocolate-peanut butter mixture over the peanut butter base. Spread into an even layer.
Refrigerate for at least one hour, or until the chocolate topping is firm.
Once set, lift out of the pan and cut into squares or bars. Store and serve chilled or at room temperature.
Notes
Store bars in an airtight container in the fridge for up to 1 week. For longer storage, wrap individually and freeze for up to 3 months.