Wash, peel, and chop your apples into small pieces, no bigger than a half inch in size.
Add the apples, brown sugar, white sugar, cinnamon, ginger, cornstarch butter and lemon juice to a large frying pan. Cook over medium heat until the apples are slightly tender and the juices of the apple combine with the butter and sugar to take on a thickened caramel consistency. Set aside to cool.
Prepare the cinnamon sugar topping by mixing together 1/4 cup of granulated sugar with 1/2 teaspoon of cinnamon.
Prepare an egg wash by whisking together the egg with 1 teaspoon of water.
Pre-heat your oven to 400°F and line two baking trays with parchment paper.
Lightly flour your work surface and place your first sheet of puff pastry on top. Gently roll the pastry into a 15 inch square. Cut the pastry into 16 squares, about 3.75 inches across (see notes below).
Transfer the pastry squares to your parchment lined baking tray and brush a thin coat of egg wash onto the tops of each one.
Drop a spoonful of the apple filling onto the centre of each square.
Fold each pastry into a triangle shape, by taking one corner of the pastry and folding it over the filling until it touches the opposite corner. Use your fingertip, or the prongs of a fork, to crimp the edges of the pastry down along the edge and seal the filling inside.
Brush the tops of each apple turnover with more egg wash.
Sprinkle a generous amount of the cinnamon sugar mixture on top of each one.
Make sure the turnovers are spaced out 1-2 inches on the baking tray, then bake at 400°F for 16-18 minutes until the pastry is golden brown and crispy.
While the first batch of pastries are in the oven, repeat the above process with the second sheet of puff pastry.
Serve warm and enjoy!