Working ahead, make and chill crust. In a large bowl, whisk together the flour, sugar, and sea salt. Use a large hole, coarse grater to grate in half of the the butter. Use the slicer on the box grater or a sharp knife to cut remaining butter into paper thin slices. Use your fingertips to blend butter into the flour, flattening out any large bits as you go. Using a silicone spatula, drizzle half the water over the mixture. Continue adding water in 1 tablespoon increments, just until the dough easily holds together. Divide dough into two equal discs, flatten, cover with plastic wrap, and chill for at least 30 minutes or up to 5 days.
When ready to cook the pie, preheat oven to 425 degrees F, slide a rimmed baking sheet into the oven, and let that get nice and hot too. On a lightly floured surface, roll out bottom crust to a 14-inch circle. Press into buttered pie pan (preferably metal or heat and cold resistant glass) and trim all but 1-inch of overhanging dough. Set pie pan into the fridge while you prepare the filling. (Reserve, wrap, and chill any leftover dough for the lattice.)
Incorporating any leftover dough, roll dough for top crust out into a 14-inch circle. Cut dough into 6 - 8 (2-inch wide) strips. Once dough is ready, remove bottom crust from fridge. Working quickly, spoon filling into crust (leaving out juices at the bottom will help to avoid a soggy bottom crust). Weave lattice according to these instructions and crimp edges. Bush lattice with egg and sprinkle with sugar.
Place pie on preheated baking sheet. Bake 15 minutes at 425 degrees F. Rotate pie and turn heat down to 350 degrees F. Bake another 40 - 45 minutes, or until pie is a deep golden hue and filling is hot and bubbly. If crust seems to be baking too quickly, shield edges with tin foil.