In a small bowl, dissolve the cornstarch in 1/4 cup of the cold water. In a saucepan over low heat, warm the blueberries, cornstarch, remaining water, sugar, and wine. Cook for 15 minutes, or until the blueberries are soft. Set aside for 10 minutes to cool. Process the blueberry mixture in a blender or food processor until all of the ingredients are incorporated and smooth. Chill in the refrigerator. Before serving, add the sour cream and stir. Serve in chilled bowls.