Hot and pungent, wasabi is commonly used as a condiment for sushi and sashimi but is also useful as an ingredient in other Japanese dishes. Fresh wasabi root (also known as Japanese horseradish) is hard to find and expensive (about $8 per ounce). More widely available is wasabi that is sold in paste or powder form (the powder is mixed with water to form a paste). Because fresh wasabi root is so expensive, most pastes and all powders contain no wasabi at all, but instead a mixture of garden-variety horseradish, mustard, cornstarch, and food coloring. Nevertheless, we have found that they do the job just fine in our recipes.