Fish sauce, or nuoc nam in Vietnamese, is at once a condiment, a dipping sauce and a flavour added to Vietnamese soups and noodle dishes. And just as a wine's quality is judged on bouquet, colour, finish and "legs" on the glass, so, too, is that of fish sauce.
While you're still laughing, here's the bad news: the Vietnamese fish sauce you've been cooking with in Australia is probably the wine aficionado's equivalent of cat's pee. That's because Vietnam will not export the good stuff, keeping it all for the demanding domestic market.
There's precious little you can do about it, though. Except, perhaps, look closely next time you're in the arrivals hall. That Vietnamese lady who staggers through customs under the weight of that cardboard box is, more than likely, carrying a dozen bottles of Vietnam's finest for her friends and relations back here.
What you pick up at the supermarket or the Asian grocer is unlikely to be good quality. It has probably been made by a process of hydrolysis, whereby artificial colouring and acid have been added to enhance fermentation.
Real fish sauce takes time. The good stuff is made by fermenting long-jawed anchovies. The fish are thoroughly washed and placed into large earthenware or wooden vats that have been lined with sea salt. They are topped with more salt (roughly three parts salt to one part fish) and a large bamboo mat, weighted with rocks, is placed on top. The fish and salt are then covered with mosquito netting and the is vat sealed, before being left for several months.
The natural fermentation process draws the liquid from the fish. This is the beginning of nuoc nam, the literal translation of which is "fish water". The fish mixture is, from time to time, exposed to direct sunlight. Finally, it is strained, placed in a clean vat and allowed to air for several weeks to remove any lingering "fishy" smell.
This first draining is not unlike like the first pressing of a good olive oil - as close to pure as possible. The label of a quality sauce will say "ca com" - an indication that anchovies have been used. It will also indicate the protein level (40% is the highest available) in the sauce. Oh yes - a good fish sauce is pressed after the tops of the vats have been removed and the mixture exposed to three consecutive full moons.
Inferior sauces are made from second or third distillations, after salt water has been added to the slurry left from the first pressing.
If you tip a little of the good stuff into a wine glass, swirl it and hold it up to the light, it will cling to the glass and roll evenly down the sides - it's got legs. It should have a non-cloudy caramel colour and no acidic or fishy after-taste.
This article was published on Gourmettraveller.com.au in June 2009.