In a large bowl, combine the blueberries, sugar, vanilla, salt, lemon zest, lemon zest, and flour. Stir to combine well. Set aside.
Roll out the pie shells to fit a 9" or 10" deep-dish pie plate, about 1/4 inch or so. Place one pastry in the pie dish and prick the bottom all over with a fork. There will be some overage of the pastry, but that's ok. Fill with the blueberry mix and place the other rolled out pastry on top. Trim the edges so that there is about 1/2 inch over the sides. Working from the bottom piece, roll over the top edge and crimp to seal the edges of the pie. With a sharp knife, slit a few holes in the top. Brush the top with a beaten egg and sprinkle a couple of tablespoons of sugar over the top.
Place in a 375-degree preheated oven for 45-55 minutes or until it is golden brown.
