Preheat your oven to 425°F

Prepare the blueberry filling: In a large bowl, combine frozen blueberries, granulated sugar, corn or tapioca starch, lemon juice, lemon zest, and a pinch of salt. Mix well.

Cook filling: In a saucepan cook the filling for 15 minutes or so, until the juices release and the filling has thickened. It will continue to thicken in the oven, but you want to help it along to control the juiciness. Allow filling to cool.

Prepare the pie crusts: Roll out one pie crust to about 12 inches in diameter and place it in a pie pan without trimming the over-hang. Pour the cooled blueberry mixture into the crust.

Add the top crust: Roll out the second pie crust. Either cut into strips to make a lattice top or simply place it over the filling. Trim any excess dough and crimp the edges to seal.

Brush with egg wash: Beat the egg and brush it over the top crust for a golden finish.

Ventilation: If you didn't make a lattice top- make a few small slits in the top crust to allow steam to escape.

Bake: Put the pie in the preheated oven and bake for 45-55 minutes until the crust is golden and the filling is bubbling. Add a pie shield or round of aluminum foil if the edges start getting too golden.

Cool: Allow the pie to cool on a wire rack for at least 2 hours before serving.