Prepare the pie crust

• Roll out the chilled pie crust into about a 12-inch circle.
• Transfer to a 9-inch pie dish and trim the edge or fold the excess under.
• Cover and refrigerate while you make the filling.

Cook the apple filling

• Melt the butter in a large pot over medium heat, add the apples and mix.
• Add the granulated sugar, brown sugar, cinnamon and nutmeg, mix until combined, then lower the heat to medium-low and cook until the apples soften to your liking.
• Add the vanilla, lemon juice, flour and cornstarch and cook until the juices have reduced and thickened.

Cool the filling

• Remove from the heat and let it cool completely.

Make the crumble

• In a small bowl mix together the flour, brown sugar, oats, cinnamon and salt.
• Add the butter and mix with a fork until crumbles form.
• Set aside to firm up in the fridge.

Assemble the pie

• Preheat the oven to 375°F.
• Take the pie crust out of the fridge, combine the egg and water and brush the egg wash on the edges of the crust.
• Add the cooled apple filling, then sprinkle the crumble all over.

Bake the pie

• Place the pie on a baking sheet and cover the edges with a pie shield.
• Bake until the filling is bubbly and the crumble is slightly golden brown.
• Remove the pie shield and continue baking so the edges get nicely golden.

Cool and serve

• Allow the pie to cool so that it sets and is easier to slice.
• Serve with ice cream and drizzle caramel sauce.