To prepare the crust, give the dry ingredients a whiz in the food processor to combine. Pulse in the shortening and butter, just until evenly dispersed and pea-sized clumps form. Add 6 tablespoons of ice water and pulse, add in ad additional tablespoon of water until a dough begins to form. I usually need 8 tablespoons of water. Remove dough from food processor and separate in two round disks. Wrap in Saran wrap and chill for at least 30 minutes prior to use.
To prepare the caramel, combine the sugar and water in a large saucepan (at least 6 quart) over medium-high heat. Allow the sugar and water to cook undisturbed about 10-11 minutes until the sugar has turned a deep amber hue. Carefully and slowly add the heavy cream in, whisking all the while to combine. Please note that the caramel will bubble and steam and sputter, so be sure to add the cream slowly and with care. Continue whisking and cooking until the caramel is smooth and well combined. Remove the pan from the heat and add the salt and butter, whisking until the butter is incorporated. Set aside while you prepare your pie ingredients.
To assemble the pie, preheat an oven to 375 degrees. Prepare an egg wash by whisking 1 egg with 2 teaspoons of water. Set aside while you prepare the pie.
Roll out one half of your dough on a lightly floured surface to a 12”x17” rectangle. Once smoothed and sized, roll the dough back onto the rolling pin and transfer the dough into a 15″ x 10″ x 1″ jelly roll pan. Gently press the dough into the edges of the pan and trim off excess dough, leaving a 3/4’” overhand around all edges. Use some excess dough to fill in spots where the dough may have cracked or wasn’t long enough.
Sprinkle your prepared apples into the pan and spread out to fill evenly. Drizzle the caramel over the apples, being sure to distribute it evenly. You can re-warm the caramel slightly if needed.
Roll out your remaining piece of dough to a 12”x17” rectangle. Roll the dough onto your rolling pin and transfer it to the pie. Center the pie top on the pan and fold the bottom edge over the top, crimping with your fingers as desired. Use a knife to vent the pie and brush the egg wash over the top crust. Bake in the preheated oven for 50-60 minutes, or until the top is golden brown and the caramel inside is bubbling. Rotate the pie during baking as needed to brown evenly.