Make the Homemade Pie Crust. Chill the dough for 1 hour (or up to 24 hours).
Meanwhile, stir together the blueberries, granulated sugar, cornstarch, maple syrup, lemon juice, lemon zest, cinnamon, vanilla extract, and salt in a saucepan and heat over medium heat for 4 to 5 minutes, stirring frequently, until the sauce is thick. Transfer the blueberries and sauce to a bowl and cool at least 30 minutes, until the crust is ready.
Preheat the oven to 425°F. Place a rack in the lower third of the oven with a rimmed baking sheet covered in foil to preheat.
Grease a 9” standard pie pan.
Dust flour over a clean work surface. (Or if you have a pastry cloth, set it up and dust it with flour.) Dust a rolling pin in flour. Place one ball of dough on the work surface and gently roll it evenly from the center to the edge, until the dough is about ⅛-inch thick. Pick up the dough and rotate it occasionally as you work, keeping as perfect of a circle as possible and making sure it’s not sticking to the work surface. If it’s sticking, dust with a bit more flour. Roll the dough to a 12-inch wide circle (which corresponds to the 9-inch circle on a pastry cloth). Visible chunks of butter are expected: that’s what makes it flaky!
Gently drape the dough over then rolling pin, then transfer it the prepared pie pan. Gently center and push the pastry towards the bottom of the pan.
Allow the 1-inch of overhanging dough to drape over the edge. Fill the dough with the blueberries and sauce and place the entire pan in the freezer while rolling out the next dough.
Roll out the second dough ball. Use a pizza cutter to cut the dough into 1 inch strips. Remove the pie from the freezer and weave a lattice pattern using the strips (see this video for a demonstration). Use kitchen scissors to cut off excess from the strips, then fold the draped dough over the top and crimp the edges with a fork.
Whisk the egg in a small bowl, then brush the top of the lattice and crust with the egg wash using a pastry brush. Sprinkle generously with turbinado sugar.
Place the pie directly onto the preheated baking sheet lined with foil. Bake immediately for 15 minutes (at 425°F). Leaving the pie in the oven, reduce the oven temperature to 375°F and bake for 60 minutes, until browned and the filling has small bubbles. Check at 40 minutes and if necessary, add a foil tent if the crust is already very golden brown.
Cool at least 2 hours, then refrigerate until ready to serve. Bring to room temperature before serving.