A vibrant green paste made from the ground root of a type of horseradish. Served with sushi, it is very hot and pungent, rather like mustard, so is only used in minute quantities to serve with raw fish and shellfish in sashimi and sushi. It is also delicious mixed into butter to serve western-style with a grilled steak. You can buy tubes of wasabi paste or powdered wasabi, which is mixed with water to make a paste.