I spooned the sauce over a mix of blueberries, raspberries, blackberries, and strawberries…and made it even more special by serving it all in martini glasses. Delish!!!!Beat 1/3 cup butter, softened, and 1 cup powdered sugar at medium speed with an electric mixer until smooth. Add ½ cup sour cream, ½ teaspoon lemon juice, and ¼ teaspoon vanilla, beating until creamy. Cover and chill until ready to serve (up to 8 hours). Makes about 1 ¼ cups.