dashima, dasima, haidai, kelp.
Kombu is a type of thick flat seaweed cultivated in the northern waters of Japan. Although it may sound like a plant, seaweed is technically classified as a type of algae. Kombu comes in many forms making it a versatile ingredient with uses ranging from soup stocks to wrappers and is even eaten as a snack. While it's rare to find it fresh outside the areas where it's harvested, it is dried, salted or vinegared and distributed all over the world.
What's it taste like?
Because of the high concentration of glutamic acids, a building block of MSG, kombu is filled with umami. It's not fishy at all, with a briny, almost mushroom-like flavour. The white powder on the outside is where much of the flavour is, so don't wash it off.
Where do I get it?
You can find kombu at almost any Asian grocery store in bags. Dashi kombu typically comes in small rippled sheets about half the size of a credit card. Look for uniform sheets with lots of white powder on the outside. The bigger sheets are typically for rehydrating and wrapping around things such as fish. Salted kombu comes in thin strips and is covered in salt. If in doubt check the label. Most imported foods in the US have labels translated in English. If not you can look for bags with the following symbols either 出汁 or だし
When is it best?
There's no season and dried kombu will keep for a very long time.
How do I use it?
Kombu is most commonly used for making dashi and other soup stocks. The broth it produces is very mellow with a briny umami-filled flavour that bolsters other more flavourful dashi ingredients such as katsuobushi or niboshi. In larger sheets it can be rehydrated and used to wrap seafood or meat for stewing. The salted variety can be mixed with hot rice, or be added to porridge. There are also some snack varieties that are either dried or salted and vinegared and make a good accompaniment for alcoholic beverages.
Kombu is high in Iodine, Vitamin K, Folate, Magnesium, Calcium and Iron.