Combine flour, salt, and cold butter nuggets in a food processor. Pulse into a coarse mixture.
Add cold water and pulse until mixture turns into a smooth dough.
Lightly knead the dough then wrap and chill.
Toss together the apples, brown sugar, cinnamon, nutmeg, and cornstarch in a bowl. Leave to sit for 15 minutes.
Take dough out of the refrigerator and transfer onto a lightly-floured surface.
Roll out into a 1/8β thick sheet and cut into 6 squares.
Spoon apple mixture into the center of each square.
Take pastry from one corner and fold over. Seal by crimping the edges with a fork.
Arrange pies on a parchment-lined baking sheet.
Brush with melted butter
Bake for 20 minutes at 350F.