Preheat the oven to 425°F (220°C).

In a large bowl, combine the diced apples and lemon juice. Toss to coat the apples.

Add the granulated sugar, cinnamon, and flour to the apples. Mix well until the apples are evenly coated.

Roll out one pie crust on a lightly floured surface. Use a round cutter to cut out circles, approximately 4 inches in diameter.

Place the circles onto a baking sheet lined with parchment paper.

Spoon a generous amount of the apple mixture onto the center of each circle.

Roll out the second pie crust and cut out the same size circles. Place these over the filled circles and seal the edges by pressing with a fork.

Brush the tops of the pies with the beaten egg.

Cut small slits in the top of each pie to allow steam to escape.

Bake in the preheated oven for 20-25 minutes or until golden brown.

Let cool slightly before serving. Serve warm with vanilla ice cream if desired.