Line a 12-cup muffin pan with paper liners.
Stir graham cracker crumbs and melted butter with a fork. Evenly divide among the muffin cups (about 1 1/2 tablespoons per each). Press down to compact (I use the bottom of a shot glass and it works perfect for this step).
Beat cream cheese with a hand mixer in a large bowl until smooth. Beat in sweetened condensed milk and peanut butter. Fold in Cool Whip.
Divide batter among muffin cups, about 2 tablespoons per each. Top each pie with 1/2 teaspoon of mini chocolate chips. Freeze overnight before eating.
The crust is crumbly, so it’s best to eat these right from the paper liners.