This is one of the few nigiri sushi that is served cooked. In fact you need to cook eel because consumption because see eel is mildly toxic when uncooked. (And you can avoid bei
ng zapped in the mouth) It is almost easiest to make a good anago because it always taste pretty good when cooked and the eel sauce is a tasty thick and rich sauce that will greatly enhance the flavor of the eel. The sauce is usually made out of a combination of soy sauce, sugar, salt, a bit of MSG, bonito extract...