Preheat the oven to 190°C (375°F). Line a baking sheet with parchment paper.

In a bowl, mix the diced apples with brown sugar, cinnamon, and lemon juice.

Roll the pie dough on a lightly floured surface and cut it into six squares.

Spoon the apple filling into the center of each square.

Fold each square to form a rectangle or triangle and seal the edges with a fork.

Place on the baking sheet, brush with milk, and sprinkle with coarse sugar if desired.

Bake for 18–20 minutes, or until golden and crisp.

Cool slightly on a wire rack before serving.