Easy Blackberry Jello Pie

1 cup sugar
3 tablespoons cornstarch
1 tablespoon butter
3 tablespoons blackberry Jello powder
2 cups raw blackberries, washed
1 ready-to-use piecrust, either graham cracker or regular

Directions:
Combine sugar and cornstarch in a saucepan and stir well. Add water and cook over medium heat, stirring often, until thick. Add butter and stir until melted. Add Jello powder and stir until dissolved (about 2 minutes.) Fold in blackberries. Pour into crust and chill for four hours. Serve with whipped topping.