Preheat the oven to 400F. Line a large rimmed baking sheet with parchment paper or a silicone baking mat. Set aside.
Melt butter in a large skillet over medium heat.
1 tablespoons butter
Add apples to skillet and cook for about 2-3 minutes. Apples should be beginning to soften.
2 baking apples
Stir in brown sugar and cinnamon.
1/2 cup brown sugar, 1/2 teaspoon ground cinnamon
Cook, stirring regularly, for 2 more minutes.
Stir together cornstarch and 1 tablespoon water.
1 tablespoon cornstarch, 1 tablespoon water
Add to the skillet, and mix well.
Cook for another minute, or until sauce has thickened.
Remove from heat to cool slightly.
Unfold puff pastry sheets, and press sheets back together to fix any cracks.
17.25 ounce package frozen puff pastry sheets
Cut each sheet into 4 squares.
Spoon apples onto the center of each squares. Don't spoon the accumulated juices in.
Fold over from corner to corner into a triangle shape.
Crimp edges together to seal.
Place turnovers on a baking sheet, leaving about 1 inch between them.
Sprinkle the tops with the raw sugar. You can also dust the tops with cinnamon if desired.
Bake for 20-30 minutes or until turnovers are puffed and light golden brown.
Notes
Baking apples: Any baking apple will work in this recipe. Granny Smith apples are my favorite because they're a little tart which helps to balance out the sweetness of the filling.
Butter: I use salted butter in this recipe.
Brown sugar: Light brown sugar or dark brown sugar will work in this recipe.
Cinnamon: If you want to mix up the spices, use an equal amount of apple pie spice in place of the cinnamon.