Wasabi is the pungent, pale-green Japanese condiment made by grating the stout rhizome of Eutrema japonicum, a semi-aquatic perennial of the cabbage and mustard family. Freshly grated to a fine, slightly sticky paste, it delivers a sharp, volatile, sinus-clearing heat that surges up into the nose rather than burning the tongue, then fades within minutes — the same airborne "mustard-oil" chemistry found in horseradish and mustard. It is the classic accompaniment to sushi and sashimi and a defining flavour of Japanese cuisine, prized for a heat that is clean and fleeting rather than lingering. Because the plant is notoriously difficult and slow to grow, genuine wasabi is scarce and expensive, and the great majority of "wasabi" served worldwide is in fact dyed horseradish and mustard.