• Preheat the oven to 400 degrees F. Line a large rimmed baking sheet with parchment paper and set aside.
• Combine the apple juice and diced apples in a bowl to prevent them from turning brown. Add brown sugar, granulated sugar, cornstarch, cinnamon, and melted butter to apple mixture. Stir well to combine. Set aside.
• On a lightly floured surface, roll puff pastry to a 12-inch by 12-inch square. Brush any excess flour from pastry.
• Cut each sheet into 4 squares. Place 2 squares onto prepared baking sheet.
• Brush the edges of each square with the egg wash and neatly place 1/3 cup of the apple mixture on half of the square.
• Fold the pastry diagonally over the apple mixture, pressing gently. Seal by gently pressing the edges with a fork, being careful not to make holes with the fork.
• Brush the top with egg wash, make a small slit on the top of each turnover.
• Bake for 20 minutes, until lightly browned and puffed.
• Let cool for 5 minutes.

Make the maple glaze:

• Combine all glaze ingredients in a small bowl and whisk until smooth. Drizzle over warm turnovers.