Karashi (芥子, 辛子, からし, or カラシ) is a type of mustard used as a condiment or as a seasoning in Japanese cuisine. Karashi is made from the crushed seeds of Brassica juncea and is usually sold in either powder or paste form. Karashi in powder form is prepared by mixing with lukewarm water to a paste and leaving it covered for a few minutes.
Karashi is often served with tonkatsu, oden, nattō, and shumai. It can be used as part of a dipping sauce when mixed with mayonnaise, called karashi mayonnaise or with vinegar and miso, called karashi su miso.
The whole, ground, cracked, or bruised mustard seeds are mixed with water, vinegar, lemon juice, wine, or other liquids, salt, and often other flavorings and spices, to create a paste or sauce ranging in color from bright yellow to dark brown. The taste of mustard ranges from sweet to spicy.