Preheat the oven to 425°F. Roll out the pie crusts to 1/8-inch thickness and cut out 12 circles using a 3-inch cookie cutter. Place each circle in a muffin pan cavity, pressing into shape.
Mix the chopped apples, sugar, flour, cinnamon, vanilla extract, and nutmeg. Fill each crust with the apple mixture and top with a small piece of butter.