In medium saucepan over medium low heat, combine sugar, cornstarch, cinnamon, water and 2 cups of the blueberries. Stir until sugar dissolves and mixture boils and thickens. (10 or 15 minutes) Remove from heat. Add butter, lemon juice and remaining blueberries. Stir gently until butter melts in. Let cool.
Beat whipping cream until thick. Add powdered sugar; continue whipping until stiff peaks form. Be careful not to overbeat. Spoon into pie crust and up over edges.
Gently pour cooled and thickened blueberry filling into center of pie on top of whipped cream. Cover and refrigerate until serving. Best served same day.