Cut down through back of each shrimp, cutting almost to, but not through, the underside portion. Spoon some purchased dried tomato pesto in the slit of each shrimp. Spoon some dairy sour cream into a pastry bag fitted with a small star tip. Pipe sour cream over pesto in each shrimp. Serve each on a fresh basil leaf. Makes about 20 appetizers (8 to 10 servings).