Blackberry Pie

rolled pie crusts (this is one box of refrigerated pie crusts if you buy them at the store (if making from scratch use a "double crust" recipe))

fresh or frozen blackberries (thawed if frozen)

granulated sugar (if your berries are very sour (add an extra 1/2 cup of sugar))

all purpose flour

salt

juice of 1/2 of a fresh lemon

cold butter

beaten egg mixed with 1 tablespoon water