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.
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.