Make the Crust: In a large bowl, whisk together the flour, sugar, and salt.
Add the butter and, using a pastry blender or two forks, quickly cut it into the flour until large pea-sizes bits remain.
Add ¼ cup of the ice water and use a rubber spatula to stir it into the dough, pressing it together. If it still seems dry, add more water a little at a time until it is cohesive.
Turn the dough out onto a lightly floured work surface and bring it together with your hands, then divide it into two equal portions.
Working with the first piece of dough, gently pat it into a 6-inch circle. Lightly flour the top and gently and quickly roll it out to a 13-inch circle, picking it up and doing a quarter turn after every couple of rolls to keep it from sticking.
Transfer the dough to a 9-inch pie plate and gently press it into the bottom and up the sides. Trim the dough to 1 inch beyond the lip of the pie plate.
Roll the second piece of dough out as you did the first, this time into a 12-inch circle. Gently transfer it to a parchment-lined baking sheet and refrigerate both the dough-lined pie plate and dough round while you prepare the filling.
Make the Filling: Place the blueberries in a large bowl, sprinkle with the lemon juice and toss to coat evenly. In a small bowl, stir together the sugar, cornstarch, lemon zest, salt and cinnamon. Sprinkle the sugar mixture over the berries and toss to distribute evenly. Immediately transfer to the dough-lined pan. Dot with the butter.
Carefully position the reserved dough round over the filled pie. Trim the edge, leaving 1 inch of overhang, then fold the edge of the top round under the edge of the bottom round and crimp the edges to seal. Using a small, sharp knife, cut an asterisk 4 to 5 inches across in the center of the top to allow steam to escape during baking. (You can also do decorative cutouts of the top dough as pictured above.)
Refrigerate the assembled pie for at least 2 hours.
Bake the Pie: Position a rack in the lower third of an oven and preheat to 375°F.
In a small bowl, whisk together the egg and water for the egg wash.
Brush on the egg wash over the surface of the pie. Bake the pie until the crust is golden and the filling is thick and bubbling, 50 to 60 minutes. Transfer to a wire rack and let cool completely,, at least 2 hours. Serve at room temperature. Store leftovers, covered, at room temperature for up to 3 days.