Preheat your oven to 350°F (175°C). Core and chop the apples into small pieces, then toss in a mixing bowl with sugar, cinnamon, and cornstarch. Let sit for 10 minutes.

Roll out gluten-free puff pastry into a rectangle about ¼ inch thick on a floured surface, then cut into 4-inch squares.

Spoon a tablespoon of the apple mixture onto each pastry square. Fold corners to form triangles and seal edges.

Whisk together an egg with a splash of water or almond milk for the egg wash. Brush the tops of each turnover.

Bake on a parchment-lined baking sheet for 20-25 minutes until golden and puffed.

Cool on a wire rack for about 5-10 minutes before serving warm.