This Japanese version of horseradish comes from the root of an Asian plant. It's used to make into a green-colored condiment that has a sharp, pungent, fiery flavor. Wasabi, which is also called Japanese horseradish, is available in specialty and Asian markets in both paste and powder form. The latter is mixed with water much like dry mustard. Some specialty produce markets carry fresh wasabi, which may be grated like horseradish. In Japan, sushi and sashimi are served with a condiment of wasabi mixed with soy sauce.