In a large bowl add the lemon juice and water and gently stir to combine.
Add the sliced apples into the lemon/water mixture to keep them from browning while you prepare the rest of the recipe.
Add a heavy saucepan over a medium high heat. Add the butter and allow to melt but not discolour.
Drain lemon and water from apples, and place them carefully into the hot pan.
Cook and stir for about 2 minutes until they start to take on some colour.
Add brown sugar and cinnamon, and cook for 2 more minutes. Stir continuously and you dont want anything to stick.
In a small bowl, add the corn starch and 1 tablespoon of warm water. Stir thoroughly to create a thickening agent. Add the corn starch mix to the pan and thoroughly mix.
Cook for about another minute, or until sauce has thickened.
Remove from heat and allow to cool slightly.
Unroll the puff pastry sheets. They should be perfect squares, if not give them a quick trim. (Each piece will create 4 turnovers.)
On a flat work space, cut each pastry square into 4 smaller squares.
Carefully spoon the cooler apple mixture into the edge of each square.
I like to roll, very gently, th pastry over to create a "sausage roll" kind of look.
Gently make a few thin slices in the top of the turnovers to help them grow when cooking.
Place turnovers on a baking sheet, leaving about 1 inch between them.
Place the baking tray on the preheated oven for 25 minutes.
They should have puffed up and be a light brown as in the photo.
Place on a cooling tray and allow to cool fully.
In a bowl add the sugar, milk and vanilla extract and mix well. I use a pastry brush tp coat the turnovers and add an additional sprinkle of sugar for that extra kick (optional)