Wasabi

Wasabi or Japanese horseradish is a plant of the family Brassicaceae, which also includes horseradish and mustard in other genera. The plant is native to Japan, the Russian Far East including Sakhalin, and the Korean Peninsula. It grows naturally along stream beds in mountain river valleys in Japan. Wasabi is grown for its rhizomes, which are ground into a paste as a pungent condiment for sushi and other foods. From Wikipedia