Cook 1/2 lb. fresh mushrooms (cut in half) and 1/4 cup minced onion in 2 tablespoons butter until tender but not brown. Cover tightly and cook 10 minutes over low heat.

Push mushrooms to one side; stir 1 to 2 tablespoons all-purpose flour into the butter. Add 1/2 cup heavy cream, 1/2 cup dairy sour cream, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Heat slowly, stirring constantly, almost to the boiling point. Makes about 1 1/2 cups.