Cocktail sauce in its simplest form is ketchup mixe with prepared horseradish, though in the United Kingdom, Ireland, Iceland and Belgium, mayonnaise is usually mixed with the ketchup, similar to fry sauce. Furthermore, in Belgium, a dash of whisky is often added to the sauce. It is popularly served with steamed shrimp and seafood on the half shell. Many restaurants use chili sauce in place of ketchup.