In a mixing bowl, combine the blueberries, sugar, cornstarch, and lemon juice.

Preheat your oven to 400°F (200°C).

Unroll the pie crusts on a lightly floured surface.

Using a round cutter or a bowl, cut out circles about 5 inches in diameter.

Place a spoonful of the blueberry filling in the center of each circle.

Fold the dough over to create a half-moon shape and press the edges together with a fork to seal.

In a small bowl, mix the beaten egg and milk and brush the mixture over the tops.

Place the turnovers on a parchment-lined baking sheet and bake for 20 to 25 minutes, until golden brown and bubbly.