In a saucepan, combine sugar, cornstarch and salt. Add water and mix well, removing all lumps, and add 2 cups blueberries. Cook mixture over medium heat, stirring constantly until mixture comes to a boil and is very thick. Remove from heat and stir in butter and lemon juice. Cool slightly. Place remaining 2 cups of blueberries in baked pie shell, distributing them evenly. Top with the cooked berry mixture, making sure to cover all the berries and spread it to the edges. Chill and serve with vanilla ice cream or real whipped cream.
(Jerril Matthews, Trail, British Columbia)