Source: Ye Old College Inn - Houston, Texas - from Ford Treasury of Favorite Recipes from Famous Eating Places

3 cups blueberries and juice
2/3 cup granulated sugar
4 level tablespoons cornstarch
2 tablespoons butter
Dash of salt
3 1/2 teaspoons wine vinegar

Drain juice from 3 cups blueberries. Bring juice to quick boil, then add 2/3 cup sugar, cornstarch, butter, dash of salt and vinegar. Cook until slightly thickened. Cool.

Add berries and pour into 9-inch baked pie shell.

Topping
1 1/2 cups sour cream
2 tablespoons granulated sugar
1/2 teaspoon vanilla extract

Combine sour cream, 2 tablespoons sugar and vanilla extract. Spread evenly over berries and bake in 250 degree F oven for 10 minutes. Refrigerate for at least 2 hours before serving.