Kombu is an essential ingredient in the making of Japanese soup stock called Dashi.
A strip of kombu cooked with water releases glutamic acid and mineral salts which contribute a lot of flavour to your stock. Do not wipe away the white powdery coating.
It is sold dried in flat sheets or in strips. I use it in place of bay leaves and if your soup/stews cooks for 90 minutes or more it will disintegrate and thicken your dish.
Great to cook with beans.