Peel the apples and chop into bite size pieces. Put into a pot with the sugar, a squeeze of lemon juice and about 3 dessertspoons of water and cook on a low heat until the apples have softened down.
Mash the apples into a chunky mixture, mix in the cinnamon, the sultanas and allow to cool slightly as the heat of the apples could cause the pastry to melt and go out of shape.
Roll out the puff pastry (if not pre-rolled) into squares. The size is really immaterial as this will just dictate the size of the turnover but we would recommend (5 inches X 5 inches), as a portion for one turnover.
Dust the work surface with flour and place the square of puff pastry on the surface.
Mix the egg and the milk together with a whisk to make up an egg wash and brush all around the sides of the pastry square with the egg wash.
Put a spoon of the apple and cinnamon mixture into the centre of the pastry and fold into a triangle securing one corner on another.
Using a fork dipped in flour press all the way around the edge of the pastry making sure that all of the edges are tight and secure.
Make one or two incisions with the fork on the top of the turnover and brush the entire product with the egg wash.
Bake at 180 degrees for 20 minutes until well risen and golden brown.