In a medium bowl, combine the melted butter, graham cracker crumbs, powdered sugar, and 1 cup of peanut butter. Mix until well blended.
Press the mixture evenly into the bottom of a 9 x 13-inch baking dish.
In a microwave-safe bowl, combine the chocolate chips and 1/4 cup of peanut butter. Microwave in 30 -second intervals, stirring in between, until the chocolate is melted and smooth.
Pour the chocolate mixture over the peanut butter layer in the baking dish, spreading it evenly with a spatula.
Refrigerate the bars for at least 2 hours or until the chocolate is set.
Once set, cut into squares and serve.

Variations and Tips
For a crunchy texture, try adding 1/2 cup of chopped peanuts to the peanut butter mixture. If you like dark chocolate, substitute dark chocolate chips for the semisweet chocolate chips for a richer flavor. You can also experiment with different nut butters, such as almond or cashew, for a unique take on this classic recipe. For a festive touch, sprinkle sea salt or crushed candy canes over the chocolate layer before it hardens.