Hijiki (Sargassum fusiforme, aka Hizikia fusiformis) is a dark brown seaweed that grows on rocks along the coast in the northern regions of Asia, and is an important part of a traditional Japanese diet. The kanji for hijiki are ateji, and mean "Deer-tail grass."
Hijiki is rich in dietary fiber and magnesium and also has ridiculous amounts of calcium, iron. It is also a good source of protein, iodine, phosphorus, potassium, niacin, and vitamins A, B, and C. Among the more new age-y nutrients found in hijiki are phytohormones (held to fight cancer), and alginic acid (held to cleanse the body of toxic heavy metals).
Traditionally, daily consumption of small amounts of hijiki was held to held to help women have longer, more lustrous black hair, and hijiki is still used today in several types of Japanese cosmetics.
Hijiki is hard to grow in factory farm type conditions, so it is usually still harvested the traditional way, by hand with a sickle or knife at low tide. Hijiki is then typically boiled and dried for future use, although fresh hijiki is also sold. When dried, hijiki turns black and looks like little black shreds.
Once soaked and cooked, hijiki has a very mild flavor and is quite versatile. You can mix it into your salad or casserole, add it to your soup or stew, fry it into your omelet, or use it as a topping for your rice or a filler for your rice ball.
The most common use for hijiki in Japan, however, is as an appetizer, as part of a dish called "hijiki nimono." The recipie is as follows...
Hijiki nimono - ひじき煮物
Soak the hijiki in water for 40 minutes. Soak the abura-age in boiling water for 2 minutes to remove excess oil, and then squeeze out the water. Now cut the abura-age, konnyaku, and carrot into thin strips.
Strain the hijiki and briefly sauté it in the oil. Add the water and the abura-age, konnyaku, and carrot and simmer uncovered for 2 minutes. Add the soy sauce and mirin and simmer uncovered for about 7 or 8 minutes, or until all the liquid is gone. Now either enjoy your hijiki while it is fresh and warm, or pop it in the refrigerator and serve chilled later as a salad-like appetizer.