Eating & Drinking: Fish sauce is the new salt

I DO like a nice plate of stinking, dried-up fish every now and then. I love dried, salted cod, especially when re-constituted on the fashionable bistro menu into a soft, creamy paste prepared with milk, potatoes and herbs that the French know as brandade, and the Italians as baccala alla Mantecato.

I love those little dishes of Bombay duck in Indian restaurants, the tiny dried fish bodies crunching in the mouth like a coffin's bones. I love the highly unneighbourly "off" smell and powerful flavour of blachan, a dark paste of sun-dried shrimps from Malaysia that comes in blocks that look like the devil's butter. I keep mine in an airtight glass jar, and check my watch every time I open it. Generally, it takes between five and seven minutes for Fatso, the fluffball of a cat next door, to peer cautiously over the fence.

Even better than smelly dried fish, though, is a barrel of rotten, stinking, fermented fish. I love the vile-smelling liquid that gathers at the bottom of the barrel, leached out of the fish by salt as the fish bones gradually decay into dried skeletons. After three months of sitting out in the sun, the dark liquid is filtered, bottled and left to cure until it is the colour of dry sherry.

They call it fish sauce - or rather, we call it fish sauce. Thai people call it nam pla, and the Vietnamese nuoc mam, and it is one of the most unusual and most delectable sauces to land on our tables in the past few years.

It tastes salty and fishy in a single splash, like a fetid rockpool on a hot afternoon, but it blends surprisingly easily into stir-fries and curries, adding bite to sauces, soups and salad dressings. It is the essential flavour of Thailand, allowing the lime juice to retain its tang, the chilli its bite, the lemon grass its fragrance, the tamarind its sourness and the coconut milk its creaminess.

This suddenly fashionable sauce has the same DNA as garum, the salty fermented anchovy sauce of ancient Rome. Two thousand years on, it could be the new salt.

You can taste it lurking murkily in the background of Peter Gordon's Asian-marinated roast turbot with cucumber and coriander salad. It is also there, adding complexity to Henry Harris's lobster noodles in The Fifth Floor Cook Book. And it is the secret of the vinaigrette that comes with your baby leaf salad on Qantas first- and business-class flights, thanks to chef Neil Perry of Sydney's much-lauded Rockpool restaurant.

The Rockpool dressing is a masterful blend of fish sauce, red wine vinegar, olive oil, palm sugar, tarragon, chervil and coriander. It is so moreish I had to ask for three more helpings so I could pour it over everything.

And before you think this is all funny foreign stuff, take a look at your bottle of Worcestershire sauce the next time you slug some into a Bloody Mary. Stinking rotten fish, yet again. In this case, the smelly liquid obtained from salting small anchovies is mixed with chilli, ginger, shallots, garlic, vinegar, soy and molasses, and matured in oak barrels. It's the same thing, but it's not foreign, so it probably tastes better.

But you can't use Worcestershire sauce in your Thai salad or pad Thai noodles, and I'm not sure about sloshing fish sauce into your Bloody Mary, either. Fish sauce is unique. If you have a recipe that calls for it, you can always add salt, but you will only be adding salt, not a complex essence miraculously harvested from the sea.

While both the Thai and the Vietnamese make wonderful fish sauces, I always buy Thai for the very sound and scientific reason that I like the labels more. The best belongs to the Golden Boy Brand, which features a plump, beaming baby surrounded by red and yellow sunbursts, sitting on a garishly coloured globe, clutching a bottle of fish sauce in one hand and giving a resounding thumbs up with the other. You just have to trust a label like that.

My research has even turned up a claim that fish sauce is a natural protein additive used by nature in the formation of fish bone, and that it may prolong life, retarding the ageing process. Don't you love it? The elixir of youth, the fountain of eternal freshness, lies in a bucket of rotten, stinking fish.