Make the crust dough

• Whisk the flour, granulated sugar and salt together in a bowl.
• Rub in the cold cubed butter until the mixture resembles coarse crumbs.
• Add the ice water and bring the dough together, then shape into a disc and chill.

Make the crumble topping

• Combine the flour, brown sugar, salt and a dash of cinnamon in a bowl.
• Rub in the cubed salted butter until clumpy crumbs form, then chill.

Cook the apple filling

• Melt the salted butter in the skillet with the granulated sugar, dark brown sugar, cinnamon and salt.
• Add the diced apples and lemon juice and cook until the apples soften slightly.
• Stir the cornstarch into the water and add it to the pan, cooking until the juices thicken.

Roll out the crust

• Roll the chilled dough into a round large enough to line the skillet.
• Lay it over the apples, tucking the edges down inside the pan.

Add the crumble and bake

• Scatter the crumble topping evenly over the crust.
• Bake at 190 °C until golden and bubbling.

Cool and serve

• Let the pie rest in the skillet so the filling sets before slicing.