Preheat oven to 375 degrees F. Roll out the bottom crust on a floured surface then transfer to a 9-inch regular pie plate.
Combine washed, pitted, and sliced apricots in a large bowl with the sugar, cornstarch, lemon juice, vanilla extract, and cinnamon. Toss to evenly distribute the ingredients, then transfer to the prepared pie crust.
2 1/2 to 3 pounds apricots, 3/4 cup granulated sugar, 3 Tablespoons cornstarch, 1 Tablespoon lemon juice, 1 teaspoon vanilla extract, 1/4 teaspoon ground cinnamon
Roll out the top crust on a floured surface. If making a lattice crust, slice the dough into approximately 1-inch strips and lay half of them going one direction across the pie. Fold every other strip back halfway across the pie and lay another strip going the other direction perpendicular to the first rows of pie dough. Fold the strips back into place, then fold the alternate strips back over the strip you just laid down. Add another strip and continue folding back and replacing alternate strips of dough until you have a woven lattice crust. Or just go with a solid pie crust and cut a few slits in the top for venting.
Trim and fold the edges of the crust under, crimping the edges in a decorative fashion. Brush the crust with the egg wash and sprinkle with coarse or granulated sugar.
1 large egg, Coarse sugar
Bake for 50-60 minutes or until the crust is golden brown and the filling is bubbling underneath. You may want to place a baking sheet lined with parchment paper or foil under the pie for easy cleanup in case any of the juices bubble over. Also, be sure to check your pie partway through baking and cover the edges with a pie shield if they are getting too dark too quickly.
Cool for 4 hours to set up before slicing and serving.