For the pie dough: Whisk together flour, salt and sugar and add to the food processor food processor.
Add the chilled, cubed pieces of butter to the flour mixture.
Pulse the flour and butter a several times until the mixture looks sandy.
*If not using a processor and doing by hand: rub the butter between your fingers to break the larger pieces into smaller pieces while lifting the flour butter mixture to make it more airy. Do this until it looks sandy or bread crumbs.
In a small bowl, whisk the 2 tbsp ice water with the chilled egg, reserving more ice water if the dough needs to be hydrated more.
Add the egg/water mixture to the flour/butter mixture in the food processor and pulse a few time until it just starts to form a ball of dough. If it needs more hydration, use more water, 1 tbsp at a time until desired texture.
Be careful not to overmix the dough. This dough will be silky and pliable with small butter pieces still visible.
*If by hand: mound the flour/butter mixture and form a well, pour 2 tbsp ice water/egg mixture into the well and using a metal spoon, stir into the flour mixture until it gets a little lumpy then combine with your hands, working quickly. You don't want to handle the dough too much because it will make the dough tough. Mix with your hands until the dough forms a ball and isn't sticking to the bowl. Use more ice water, 1 tbsp at a time if the dough is too dry until dough is just sticking together.
The dough should not be sticky or gluey and stick to your hands. It should be silky and a little stiff.
Divide the dough into 2 balls and flatten into disks. Wrap separately in plastic and refrigerate for at least 15 minutes. (You can start peeling your peaches for pie filling while waiting to chill). Remove one disk of dough from the refrigerator. Let it stand at room temperature for a few minutes to soften slightly.
Add 1/2 the sugars to the peaches along with, lemon juice, lemon zest, cinnamon, salt. Let the fruit mixture sit for 10 minutes to allow the juices to render.
Preheat oven to 400 degrees and put the rack low in the oven.
On a lightly floured surface, roll the dough out to a 12 inch circle, about 1/8" thick, trying to work quickly and not overwork the dough, again it will make the dough less light and flaky to more you work it.
Transfer the dough to your 9 inch pie pan with dough hanging over. Refrigerate for a few minutes while finishing the peach filling.
Remove the second pie dough disk from the refrigerator to soften slightly.
Whisk the rest of the sugars and the Clear Jel together and add it to the peach filling and juices. Toss to combine.
Remove pie shell from the refrigerator and pour the peaches and juices into the pie shell. If there is too much juice, leave some out so it doesn't overflow.
Roll second disk of dough on a lightly floured surface to a 12"-diameter circle.
Top the pie with the second dough round and trim the dough to 1/2 inch beyond the lip of the pie pan. Fold both top and bottom crusts under, flush with the edge of the pie plate and then crimp with either a fork or pinch with thumb and fingers to create a scalloped edge.
Brush the top of the pie with the egg wash and sprinkle some granulated sugar on top for sweetness and crunch.
With a sharp knife, add five 2-inch vent holes around the center top of the pie to allow the steam to escape.
Place the pie on a parchment-lined, rimmed baking sheet to catch any spills. Place it in the oven on a lower rack, and bake for 20 minutes at 400 degrees. Reduce the oven heat to 350°F and bake for an additional 30-40 minutes. If the top of the pie is getting too dark, cover with foil to prevent burning. The filling should bubble and the crust is golden brown.
Transfer the pie to a wire cooling rack. Let it cool for at least 1 1/2 t0 2 hours until it comes to room temperature. This allows time for the juices in the pie to thicken.