Preheat oven to 375°F and line a baking sheet with parchment paper.
In a medium bowl, combine the blueberries, sugar, cinnamon, nutmeg, cornstarch, and water and stir to combine.
Unfold the puff pastry and cut into four equal pieces. Place the four pieces on the prepared baking sheet.
Spoon the blueberry filling onto the center of each piece of puff pastry. Brush the edges of the pastry with the beaten egg.
Fold the pastry over the filling and press the edges together with a fork to seal. Brush the tops with the beaten egg and sprinkle with the turbinado sugar.
Bake for 20-22 minutes, or until the pastry is golden brown. Allow to cool slightly before serving.
Interesting Facts
These hand pies can be made with any type of berry.
Puff pastry is made from flour, butter, water, and salt and is very light and flaky.
The cornstarch in the filling helps thicken the juices from the blueberries and gives it a glossy finish.
Turbinado sugar gives a sweet, caramel-like flavor to the top of the pies.