A traditional dashi bouillon is made by adding Bonita flakes (Katsuo Bushi) to this Kombu (seaweed / kelp) and letting it soak into a delicious, rich, bouillon. You can also add extra ingredients such as soy sauce, sugar or shiitake to deepen the flavour. Dashi is the basis for many Japanese dishes and is so popular because of its delicious umami flavour. Umami is the '5th taste' and translates best as a savoury taste that arises from glutamate (which is abundant in both kombu and bonito flakes). Kombu is a seaweed (brown seaweed) which is mainly harvested in Japan.