Preheat the oven to 400° F, with a rack in the center of the oven.
Gently stir the blueberry mixture again to make sure everything is well combined and then pour it into the pie crust.
Cut the 1 tablespoon of butter into small pieces and scatter them over the blueberry filling.
Take the second pie dough out of the refrigerator and roll it out to a 12-inch round. You can place the dough round on top of the pie as is, or you can make a lattice-top pie crust. If you put the full dough round on top of the pie, cut a few slits in the top crust to allow steam to escape as the pie bakes.
To make a lattice-top pie crust, cut the second dough round into ½-inch strips. Place the longest strip down the center of the pie. Reserving every other dough strip to go in the other direction on the pie, lay the strips across the pie with just a little bit of space in between each one. Then weave in strips going the opposite direction on the pie.
Trim the overhang to be no more than ½-inch past the rim of the pie dish. Fold the edges of the pie under and then use your fingers to crimp as desired for a decorative edge.
Make the egg wash by whisking together the egg and 1 tablespoon milk. Brush the egg wash over the pie crust. Sprinkle with coarse turbinado sugar if desired.
Bake pie at 400° F for 20 minutes. Then place a rimmed baking sheet on the rack below the pie to catch any drips of juice and reduce the oven temperature to 350° F. Bake the pie for 40-50 minutes more, until the filling is bubbly. Check on the pie after about 30 minutes and cover it loosely with foil as needed to prevent the crust from over-browning.
Let the pie cool for at least 3 hours before slicing and serving. As the pie cools, the filling will thicken up.