Add flour, sugar and salt in a small bowl and mix thoroughly with a whisk. Then transfer to a food processor fitted with the dough blade.
Cube the cold butter and add to the flour mixture. Pulse several times until butter is about pea and bean size, variation in size is okay, but no smaller than a pea.
Turn the food processor to “on” position and drizzle cold water over the dough mixture through the water hole, as soon as the dough starts to pull together turn the food processor off. You may need to stop the food processor in between and get a spatula to get the flour at the bottom to mix up.
Turn the dough out on the counter or cutting board and shape into a disk. Wrap in plastic and rest in the refrigerator for an hour.
Preheat the oven to 400°F.
Take pie dough out of the fridge and roll into a circle about 12” in diameter, transfer dough on to a parchment line baking sheet.
Separate the egg yolk and egg white in two separate bowls, beat the egg white and brush egg white over the surface of the dough leaving 1 - 1.5” border. Refrigerate pie dough.
Peel and slice peaches into ½” wedges. Toss peaches with sugar, salt, cornstarch and cinnamon in a medium bowl.
Take the pie dough out of the refrigerator and assemble the slices in concentric circles leaving 1 - 1.5” border. Pour any juice that may have come out over the fruits.
Fold the extra dough to cover the fruit on the outer edge.
Add the egg yolk to the egg white along with a splash of milk, beat together to make egg wash. Brush egg wash on the outer crust and sprinkle turbinado generously over the crust.
Bake for 30 - 35 minutes until golden brown.
Remove from the oven and let cool completely on a wire rack, about 2 hours.
