Preheat oven to 350°F (175°C). Grease a 24-cup mini muffin pan.
Prepare the pie crust pastry as usual. Roll the pie crust dough to about 1/8-inch thick. Use a 2 & 1/2-inch round cutter to cut out 24 rounds. If necessary, gather and re-roll the dough one time.
Carefully place one dough round into each muffin cup, lightly pressing it down to cover the bottom and sides.
Mix together the cooled butter, sugar, brown sugar, egg, vanilla, and salt until thoroughly combined.
Mix in the flour.
Stir in the chocolate chips.
Divide the filling evenly among the pie crusts, filling each almost full.
Bake 20-25 minutes, or until the crusts are browned and the filling is set.
Cool in the pan on a wire rack for 10 minutes. Then carefully transfer the pies to a wire rack to cool completely.