To begin, line your muffin tins with paper liners and set those aside for now.
In a mixing bowl, combine the graham cracker crumbs, 1 cup of peanut butter, powdered sugar and melted butter. Whisk until smooth.
Scoop the peanut butter mixture by rounded tablespoons into each cup, dividing it fairly evenly.
Press the peanut mixture into the bottom of the cups with the back of a spoon.
In a heat-safe bowl, combine the remaining peanut butter and the chocolate chips.
Place the bowl over a saucepan with an inch or so of water over low heat. Most people don't have double boilers now-a-days, but this is an easy way to make one. Stir the chocolate over the heat until it is melted and smooth. Remove it from the heat.
Spoon the melted chocolate over the tops of the peanut butter mixture. Cool completely and then refrigerate for at least an hour.
Store in an air-tight container in a cool place.
Enjoy!
Notes
You can also prepare this in a 9x13 baking pan instead of as cups. After it has chilled, cut it into small squares with a sharp knife.