Roll out prepared pie crust a little larger to fill a 10" pie pan. Bake pie crust according to directions and cool.
Combine sugar, cornstarch and salt in large saucepan. Add water and 2 2/3 c. blueberries; cook over medium heat, stirring constantly, till mixture comes to a boil. This will be very thick. Remove from heat and stir in butter and lemon juice. Cool in refrigerator about 1/2 hour.
In pie shell, spread about 1/2 c. of cooked berry mixture. Pour in the rest of the fresh blueberries. Top with the rest of the cooked berry mixture. Chill. Spread with sweetened whipped cream or Cool Whip and garnish with fresh blueberries.