• Preheat oven to 400F (205C) and line two baking sheets with parchment paper. Set aside.
• Begin preparing apple filling by combining chopped apples, brown sugar, butter, cornstarch, cinnamon, and salt in a medium-sized saucepan over medium-low heat.
  3 cups (350 g) cored, peeled, and diced apples, ⅔ cup (133 g) light brown sugar, 2 Tablespoons (30 g) unsalted butter, 2 teaspoons cornstarch, ½ teaspoon ground cinnamon, ⅛ teaspoon salt
• Cook, stirring frequently, until butter is melted. Increase heat to medium and continue to cook, bringing mixture to a simmer. Simmer for 5 minutes, stirring occasionally. Mixture should thicken slightly.
• Remove from heat and stir in vanilla extract. Allow mixture to cool until no longer warm to the touch before filling pie dough.
  ½ teaspoon vanilla extract
• Prepare the pastry: If using homemade pie crust or homemade puff pastry: divide the dough in half. Roll out one half onto a clean, lightly floured surface into a rectangle between ⅛”-¼” thick. If using store-bought puff pastry: unfold one sheet at a time and gently roll as needed to smooth the seams and create enough surface for your turnover squares.
  2 batches pie dough or 2 sheets puff pastry
• Using a pizza cutter or sharp knife, neatly cut dough into 4 ½” squares and transfer to a parchment paper lined baking sheet. Repeat with remaining pastry (Note: you will need to gather the scraps and re-roll them out to make all 10 turnovers).
• Prepare egg wash by whisking together egg and water. Use a pastry brush to lightly brush the surface of each pastry square with egg wash.
  1 large egg + 1 teaspoon water
• Portion about 1½ Tablespoons of filling just off center of each square. Gently fold over one corner to touch the other to envelope the apple filling. Use the tines of a fork to press and seal the turnovers. Repeat with remaining turnovers.
• Brush the outside of each turnover lightly with egg wash and sprinkle with coarse sugar (or regular granulated sugar), if desired. Use a sharp knife to cut 2-3 small slits to vent.
  2 Tablespoons coarse sugar
• Transfer to center rack of 400F (205C) oven and bake for 25 minutes, until pastry is beginning to turn golden brown.
• Allow to cool before topping with icing (if desired).

Vanilla Glaze

• Whisk together powdered sugar, 1 Tablespoon of milk, and vanilla extract. If mixture is too dry, add additional milk, a splash at a time, until mixture ribbons off the spoon.
  1 cup (125 g) powdered sugar, 1-2 Tablespoons milk, ¼ teaspoon vanilla extract
• Drizzle glaze over cooled turnovers, and enjoy.