Combine all sauce ingredients in a medium saucepan. Bring to a boil on medium-high heat. Reduce heat; simmer for 10 minutes or until onion is tender and sauce thickens slightly, stirring frequently. Cool; refrigerate until cold. Fill a large bowl with crushed ice; place bowl of cocktail sauce in center of ice. Arrange shrimp on ice around bowl of sauce. Makes 12 servings.