Many restaurants, especially in the U.S., serve wasabi. But most of it isn’t real wasabi -- it’s a mixture of horseradish and wasabi root with mustard flour, oil, vinegar, high-fructose corn syrup, and food coloring. The real thing comes from the root-like stem of a plant related to cabbage and cauliflower. It naturally grows in cool, moist places and can be pretty hard to come by and harvest. You have to grate the root as you eat it because the flavor usually only holds for about 15 minutes after grating.