Preheat Oven and Prepare Muffin Tin:

Preheat your oven to 375°F (190°C). Grease a muffin tin with butter or non-stick spray.

Roll and Cut the Dough:

Roll out the pie crusts on a lightly floured surface. Using a 4-inch round cookie cutter, cut out 12 circles for the muffin tin cups. Place each circle into the muffin tin, pressing gently to form small crusts.

Make the Apple Filling:

In a large bowl, combine the diced apples, granulated sugar, brown sugar, cinnamon, nutmeg, flour, and lemon juice. Toss until the apples are evenly coated.

Fill the Mini Pies:

Spoon the apple mixture into each dough cup, filling just to the top. Drizzle a small amount of melted butter over each pie.

Create Lattice or Top Crust (Optional):

If desired, use any remaining pie crust dough to create a lattice or full top crust on each mini pie.

Egg Wash and Bake:

Brush the tops of each mini pie with the beaten egg to create a golden finish. Bake for 20-25 minutes, or until the crust is golden brown and the apple filling is bubbling.

Cool and Serve:

Allow the pies to cool in the tin for about 10 minutes, then transfer them to a wire rack. Serve warm or at room temperature.