To make the crust: Prepare the dough as directed, dividing it into two pieces: 2/3 of the dough, and 1/3 of the dough. Roll out the larger piece and line a 9" deep-dish pie pan. Place the lined pan in the refrigerator. Roll out the second piece and cut 1 1/2" strips to make a wide lattice. Weave the lattice on a parchment circle, put it on a plate, and chill., To make the filling: Squeeze the grapes into a large bowl, separating the flesh from the skin. Reserve the skins in a separate bowl. Place the pulp in a 2-quart saucepan and bring to a simmer over medium heat. Simmer until the grapes have broken into juice, about 10 minutes. Mash with a potato masher to move this process along., Remove the seeds by straining the grape flesh mixture into the bowl with the skins, pressing firmly to extract all of the juice. Cool the grape mixture completely. Once cool, whisk the sugar, cornstarch, and salt together in a small bowl. Stir into the grape mixture, then stir in the vanilla., Pour the filling into the lined pie pan. Place the lattice over the top, folding the lattice pieces under the edge of the bottom crust. Crimp the edges, then chill the pie for 10 to 15 minutes., Preheat the oven to 425°F, preferably with a baking stone on the bottom rack., Brush the top and edges of the crust with the beaten egg and water, and generously sprinkle with turbinado (or Demerara) sugar., Bake the pie on the stone (or on your oven's bottom rack) until the crust is golden brown and the filling bubbles up through the edges, 40 to 45 minutes. Check the pie after 30 minutes and reduce the temperature to 375°F if the crust is browning too quickly., Remove the pie from the oven and cool it completely before slicing., Store any leftover pie under a cake cover, or loosely covered, at room temperature for several days; freeze for longer storage.