Wasabi, Wasabia japonica, Cochlearia wasabi, or Eutrema japonica) is a member of the Brassicaceae family, which includes cabbages, horseradish and mustard. Known as “Japanese horseradish”, its root is used as a spice and has an extremely strong flavor. Its hotness is more akin to that of a hot mustard rather than the capsaicin in a chili pepper, producing vapors that stimulate the nasal passages more than the tongue. The plant grows naturally along stream beds in mountain river valleys in Japan.
Wasabi is generally sold either in the form of a root which must be very finely grated before use, or as a ready-to-use paste (either real wasabi or a mixture of horseradish, mustard and food coloring), usually in tubes approximately the size and shape of travel toothpaste tubes. The paste form is usually just horseradish, since fresh wasabi is extremely perishable and more expensive than horseradish. Once the paste is prepared it should remain covered until served to protect the flavor from evaporation. For this reason, sushi chefs usually put the wasabi between the fish and the rice.
Fresh leaves of wasabi can also be eaten and have some of the hot flavor of wasabi roots.
The burning sensations it can induce are short-lived compared to the effects of chili peppers, especially when water is used to remove the spicy flavor.
Wasabi is often served with sushi or sashimi, usually accompanied with soy sauce. The two are sometimes mixed to form a single dipping sauce known as Wasabi-joyu. Legumes (peanuts, soybeans or peas) may be roasted or fried, then coated with a wasabi-like mixture; that can be eaten as a snack.
You can find authentic Japanese Wasabi on many Japanese Restaurants in Los Angeles.