This recipe and two others were originally posted in February 2011.
See this post:
Notes on fat choi ('hair vegetable' - nostoc flagelliforme are included at the bottom of this post for your reference.
For all my posts on Chinese New Year (春節) please see this string of posts:
The Whole New Year Thing
And note that this receipe will appear therein.
HO SI FAT CHOI 好事發財
Restaurant style dried oysters with black moss.
A dozen dried oysters (蠔豉 ho si).
8 black mushrooms (冬菇 dong gu).
A small handful (about half a 兩) of black moss (髮菜 fat choi).
Half cup superior stock.
Two TBS oyster sauce.
One Tsp. sugar.
One Tsp. sesame oil.
One Tsp. cornstarch mixed in a tablespoon water.
Soak the black moss, dried oysters, and shiitake separately for an hour or so. Rinse the black moss and the oysters to remove sand or grit.
Drain the mushrooms, reserving the liquid.
Briefly stirfry the soaked oysters, add the mushrooms, chicken stock, oyster sauce, sugar, mushroom soaking water, and fatchoi. Simmer until the mushrooms are soft. Add in the cornstarch water and sesame oil, stir till slick, and plate it.
Garnish with cilantro or spring onion.
日本蠔豉 (yat bun ho si): The best kinds of dried oysters come from Japan (日本), are nicely plump, show no damage, and are even and regular in appearance. As usual, you get what you pay for - it's worth spending a bit more.
髮菜 (fat choi): Nostoc flagelliforme.
好事發財 (ho si fat choi): 好 ho: good; to love. 事 si: matter, affair. 發 fat: issue, send out, bring forth, occur, happen. 財 choi: money, wealth. 發財 fat choi: get rich.
Nostoc flagelliforme, called hair vegetable in Chinese (髮菜 fat choi), is a cyanobacterium which grows low to the ground in arid regions. Because harvesting it is labour intensive, and the supply is naturally limited to begin with and getting more so due to high demand, it tends to be expensive. Prices vary between four and ten dollars per tael.
[TAEL: 兩 or 两 (leung): 37¾ grammes ~ 1.3 oz.]
The hair-like strands of black moss resemble steel wool in appearance and general dimensions, and are a dark green that verges on black when dry, dull greenish when wet. Lower grades are often adulterated with a dyed starch-strand imitation that appears jet-black and darkens the soaking water, and bargain black moss may in fact be mostly or entirely ersatz.
Black moss needs to be soaked for a few hours, and well-rinsed to get rid of sand, before use. If blanched in boiling water after rehydrating, the cooking time is shortened.
It is available in packets of one or two taels. Sealed against moisture it will keep for well over a year.
As a food it has no nutritional value whatsoever, is not really digestible, and is in fact mildly toxic, containing an amino acid which could adversely affect the normal function of nerve cells, possibly leading to dementia.
That does not appear to have significantly impacted anyone I know, and one would probably have to consume quite a bit for that ill-effect to be a problem for anyone other than the very rich and self-indulgent.
One minor benefit is that it helps the stomach cope with food impurities.
Black moss is used primarily for texture and appearance, and soaks up the flavours of sauces very nicely.
What makes it exceptionally desirable, especially for dishes served at New Year or at celebratory events, is that the name in Cantonese is homophonous with the term for getting rich.
Combined with dried oysters (蠔豉), the term for which sounds precisely like 'good affairs' (好事), you get the phrase 'ho si fat choi' - 好事發財 - expressing the wish that business should flourish.