Okay, as cooking challenges go, this isn't one. But I guarantee, if you haven't had mustard prepared in this way, you have no idea what the stuff tastes like. The flavor of mustard takes some minutes to develop and goes off after a few hours. Heat will reduce the flavor. Acid ingredients such as vinegar will alter the taste significantly, but help preserve it in long-term storage.

The use of mustard dates to antiquity. The name is derived from the Latin mustum ardens which means "I enthusiastically ream your sinuses with a huge auger". Or something. Like horseradish, there's a powerful physical sensation localized in the sinuses, but neither the taste nor the pain persists or affects subsequent flavors.

The complex characteristics of mustard are due to enzymes that are released (or inhibited) by water at various temperatures. Enzymes are proteins made by living cells which control the speed of chemical reactions involved in metabolism, without themselves being altered in the process. Scientists invented enzymes when we wouldn't let them blame soured wine on the pixies any more.

Mustard has other interesting properties. Importantly, it helps to form and maintain emulsions. An emulsion is a mixture of oil and water (no, really!), usually a delicate and uncomfortable compromise where little globules of the latter hang suspended in a soup of the former. Mayonnaise is an emulsion, and a little mustard in the mix not only helps it structurally, it also enhances the flavor and acts as a preservative.

The familiar commercial yellow hotdog mustard is made from white (also called yellow) mustard, which has a naturally mild flavor. Hot mustards are made from brown or oriental mustard. There's also a black mustard, but nobody makes anything out of it any more, so just forget about it.

But is it Chinese?

Hot mustard is especially nice on heavy, greasy food, such as my all-time favorite junk food: Peking ravioli, aka Chinese dumplings, aka potstickers. The commercial variety is made with vinegar, starch, turmeric (for color) and capsicum (presumably to restore the hurting that would otherwise be lost in processing and storage). American Chinese takeout always includes at least one packet of hot mustard.

I was distressed to learn that it is not only difficult to find Chinese dumplings in Chinese restaurants in England, it's impossible to find Chinese mustard. So I headed out for the ultimate authority, the inestimable Wing Yip. Wing Yip is less a Chinese restaurant supply houses than it is...the Disneyland of Chinese restaurant supply houses.

It's a gigantic Chinese shopping complex, with rice by the pallet and hoi-sin sauce by the gallon, jelly grass drink, pork balls and frozen pig uterus, cutting boards made from whole tree sections and wicked, evil looking cleavers forged from single great lumps of metal.

So I sidle up to the nice man at Wing Yip and ask whether he has any mustard. Everyone knows you have to shout at foreigners to make yourself understood. Since we were both foreigners in London, we spent a cordial few minutes grinning and yelling at each other.

"Do you have mustard?"
"Mushroom?!" "Mustard!!"
"Mushroom?!?" "Mustard!!!"
"Mushroom?!?!" "Mustard!!!!"

"Oh! Mustah!? Yellow? That mustah? No, we don't have mustah." I explain to him (at the top of my lungs, natch) that hot mustard is a staple of Chinese food in America, and he makes a smiling, chopping, oh-you, g'wan-get-outta-here gesture.

"Awwww..." he says, "they mess everything up in America."