Located in Kagawa Prefecture, Yamasei is passionate about producing high quality karashi mustard. Their "Oni Karashi" or "Demon Mustard" combines a high level of spiciness with great flavor. Yamasei produces it using Barukan (Vulcan in English) mustard seeds, the most prized and dear of the three main sub-varieties of Asian Mustard Seed. To ensure stable supply and quality, Yamasei contracts directly with farmers in Canada (the world's largest exporter of mustard seeds...if you have mustard in your fridge, the seeds were most likely grown in Canada).
There's a bit of food magic when it comes to mustard. The enzyme in mustard that helps create the spicy flavor is very volatile and can dissipate at temperatures over 70℃/158℉. So Yamasei takes care and employs great skill to control the temperature when extracting the oil from the mustard seeds and then grinding them. Then it is your job to mix the Oni Karashi mustard powder with lukewarm water (ideally between 104-140℉ -- hotter and it will turn bitter!), stir gently (traditionally in only one direction) and wait between 5 to 15 minutes. The resulting mustard will hit you with both sinus-clearing heat and great mustard taste, complementing whatever you're serving it with.
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