Roll one of the doughs out into a roughly 12-inch circle that is about ¼-inch thick. Carefully press the dough into your pie dish/tart tin & store in the fridge while you prepared the filling.
Preheat the oven to 220C.
Now, the filling. Add the lemon juice & granulated sugar to a large bowl, & toss the apple slices around in it. Add in the flour, cornflour, spices, & the brown sugar. Gently stir to coat, & set aside.
Remove the rested pie dough from the fridge & evenly layer the apple slices into the dish, fitting in as many as possible, & being sure to leave behind any juices left in the bowl. Evenly spread the caramel sauce over the top of the apples & set back into the fridge while you prepare the top of the pie.
Roll out the second pie dough on a lightly floured surface until about ¼-inch thick. Cut the dough into long strips that are 2-inches thick. Remove the pie from the fridge & cover the caramel apple filling with the strips, or make a lattice top. Crimp the edges of the pie together to seal it closed & slide the whole thing into the freezer for 15-minutes to firm up before baking.
Once chilled, brush the top of the pie with the beaten egg & sprinkle the top of the crust lightly with some sea salt. Bake in the preheated oven for 45-50 minutes, until the pie is a deep golden brown & the juices are bubbling. Leave to cool slightly before serving.