If you're using the apple corer and slicer you'll end up with apples that look like round accordions.
Therefore, at this point you'll need to slice each apple in half so that you and up with apple slices for the pie.
If you're not using an apple corer and slicer: peel the apples, core them, and slice into thin slices.
Place the apple slices in a large bowl.
Mix the sugar cornstarch, salt and cinnamon together until fully blended.
Add to the apple slices and toss until fully covered.
Preheat the oven to 425°F.
Divide the dough in half, and roll out one piece at a time.
When you roll the dough on your work surface make sure that it you’ve lightly floured the surface so the dough doesn't stick to it.
Use a thin, flexible, metal spatula to assist in lifting up the dough round and placing it into your pie pan.
I find that using a very thin plastic cutting board assists in lifting up the dough round by slipping it under the round.
This way it won’t tear as you lift it up to place into the pie pan.
When you roll out the dough make sure that it's a wide enough round to fit into your pie pan.
Roll out your second dough round. Again, make sure that it's wide enough to fully cover the pie pan.
Place the apple slices into the pie pan and spread evenly. Drizzle any remaining juices left in the bowl on top of the fruit.
Again, use a flexible metal spatula, along with the thin flexible plastic cutting board to lift up the second piecrust and placed atop the pie.
Use your fingers or the tongs of a fork to crimp the edge of the piecrust.
Cut off any excess piecrust using a sharp knife.
Use a small silicone baster to spread the beaten egg atop the piecrust.
Sprinkle the top of the piecrust with cinnamon sugar, as desired.
Use a sharp knife to puncture air holes into the top of the piecrust before placing the pie in the oven.
I usually bake my pies on top of a baking sheet so that any apple juice bubbling out will fall atop the baking sheet and not the oven.
Bake at 425°F for 15 minutes, then lower the temperature to 350°F and bake for an additional 30 to 45 minutes.
Once the pie crust is golden and the apples are just tender the pie is done.
Remove from the oven, cool, and serve.
I like to serve apple pie warm with a scoop of ice cream or drizzled with fresh heavy cream, but it's delightful just on its own.