• 800g of apples cut into cubes. Granny Smith or any other sour apple.
• 5 tablespoons of cornstarch
• 2,5dl of water
• ½ tsp cinnamon 
• Juice of ½ lemon
• 2dl sugar or brown sugar (depending on how sweet you want it)
• Pie dough

Place the chopped apple, sugar, lemon juice and cinnamon in a large saucepan and turn the heat to medium. 
In a small bowl, mix the cornstarch with the water until it has completely dissolved, then pour this mixture into the pot with the pineapples and stir. As it boils, the mixture thickens almost like a porridge. 
Keep cooking the mixture until the apple bits are tender and cooked through. 10-20 minutes depending on what sort of apple you use and how big the cubes are. Add a little more water if the sauce gets a bit too thick. Remove it from the heat and allow it to cool. 

The pie dough
Important: The filling needs to be cool enough to touch when added to the pie crust.
Roll out half the dough so it is about 5 mm thick and line the pie dish with it. 
Pour the filling over it. Roll out the rest of the dough and make a lid. Cover over the filling and cut a small vent on the top. Trim the excess dough from the edge of the pie and press down on it to form a seal between the top and bottom halves. Crimp the edge of the dough with your fingers, then brush the top surface of the pie with the beaten egg yolk.
Bake the pie in a preheated oven at 170ºC for 50 to 60 minutes.
When the pie is ready, it will have a golden crust and the filling will be bubbling. Let it cool before cutting into it. You can eat it before but it will be messy.

Tip: You can make the filling a day in advance to save time. It can also be frozen for a couple of months.