Japanese horseradish. It is most famous in form of a green paste used as condiment for sashimi (raw seafood) and sushi. However, wasabi is also used for many other Japanese dishes. Wasabi is a root vegetable that is grated into a green paste. In supermarkets, wasabi is widely available as a paste or in powder form. Wasabi powder has to be mixed with water to become a paste. Wasabi has a strong, hot flavour which dissipates within a few seconds and leaves no burning aftertaste in one's mouth.