First we will do the crust:
Chill your butter. I like it stick it into the freezer for a few minutes while I am prepping. The colder, the better!
Stir together the flour, sugar and salt in a large mixing bowl. Using your hands or a pastry blender (we think hands are fun!), smash the butter and the flour mixture until most of the butter is incorporated. You'll have some chunks of butter coated in flour. It will look lumpy and dry, which is what you want. The butter chunks are what make that flaky crust!
Drizzle the ice water and vinegar into the flour/butter mixture. Use your hands or a pastry blender to mix this together until everything pulls together into a dough. Knead the mixture a few more times until you've got a nice, smooth ball. Cut the dough into 2 equal parts, roll each into a ball and wrap individually in plastic wrap or a ziplock.
Now, here is the deal. You can do this step a couple of days out and store in the fridge, or the day of. It needs to chill for at least an hour to firm up, two is optimal.
While your dough is chilling, we will make the pie filling!
Core your apples and then slice into thin slices (See the recipe notes for the easiest way to do this!)
In another large mixing bowl, toss your apple slices, half of the sugar, brown sugar, flour, vinegar, cinnamon and a pinch of salt. Set this mixture in the fridge until your dough is ready.
Once your dough has chilled, go ahead and beat the egg and water in a small bowl, just enough to blend. (This is your egg wash. It gives the crust that delicious golden sheen!)
Preheat your oven to 375º.
Remove one of your dough balls and roll it out on a lightly floured surface. You want a circle about 12 or 13 inches in diameter, to allow room to overlap.
Carefully wrap the dough around your floured rolling pin to make transport easier. Gently lay the rolled-out round of dough to a 9" pie dish, allowing the dough to slump down into the bottom and up over the sides.
Scrape your apple filling into the pie crust (make sure you get all of those yum juices!).
Brush egg wash around the outer edges of the crust.
Roll out the remaining disk of dough and place it on top of the filled bottom crust. You could get fancy here and cut your top crust into strips for a basket-weave, etc. Most of the time, I prefer to just keep it simple!
Press the edges of the top crust to the edges of the bottom crust to crimp and seal. I like to roll them upward and tuck/crimp to make sure the pie stays together.
Place your pie on a baking sheet (I like to put a piece of parchment over it) to catch any drips from baking.
Using a pastry brush, coat the pie all over with egg wash mixture. Sprinkle it with the remaining sugar (I like to add a dash more cinnamon here, but you don't have to!). Using a sharp knife, cut a few slits in the top of your pie to allow it to vent while baking.
Place the pie into the oven, and put a pie crust shield on if you have one (you can make one out of foil if you don't! This will keep your edges from burning).
Bake the pie for about an hour and 15 minutes, until it is golden brown and the juices are bubbly. It's really important to make sure you don't underbake it! I remove the crust shield at this point and bake about 10 more minutes.
Allow the pie to rest on the counter for a half hour or so before serving. This gives the juices time to settle.
We like to drop a big fat scoop of vanilla ice cream on top!
When making this pie, you can chill it, unbaked, overnight and bake it the next day to make things go more smoothly. Just don't forget to add the egg wash before baking.
You can also fully bake it the day before and serve it at room temperature or warm it back up in a 350° oven for 30 minutes.