Preheat oven to 350. Lightly spray a 9" pie plate with non-stick cooking spray.
Roll out both of the pie crusts on a floured surface. Place one of the crusts into the base of the pie plate.
In a large bowl, toss together the blueberries, sugar, cornstarch, lemon juice, lemon zest, cinnamon, cardamom, and salt. Mix well.
Gently pour the blueberry mixture into the crust in the pie plate and add the butter pieces evenly around the blueberries. Add the top crust and seal up the the edges of the crusts and pinch together. Add a few decorative slits into the top crust layer. Then brush with the beaten egg and sprinkle the coarse sugar over the top. Place the pie plate on a baking sheet, in case any bubbles out. (You don't want it to burn on your oven floor!)
Bake in the preheated oven for 50 to 60 minutes.
Let cool completely for about 2 hours on a cooling rack.
Serve Blueberry Pie at room temp or chilled, with large dollop of ice cream.