''It's not an easy concept to get your head around. Many chefs don't get it but once you do get it, you never go back,'' Best says. In the process, the protein cells of the most delicate fish barely change, leaving its flesh cooked even though it looks raw. The cartilage of the toughest brisket can be melted so it reaches a state of tenderness usually associated with fillet. Even a watermelon can be prepared sous vide to hype its flavour.

Food prepared sous vide (under vacuum, in French) is sealed in plastic. The absence of air lowers its boiling point, allowing proteins to be coagulated at a much lower temperature. Often, the portion will be cooked in a bain marie, where a thermostat maintains the water temperature at levels precise to 0.1 of a degree. Alternatively, a steam, or combi, oven is used. Sometimes, it's just the act of vacuuming that achieves the desired result of infusing flavour. Just one mint leaf can flavour a dish of vegetables. It is one part of a huge arsenal of techniques embraced by the chef-scientists who are dominating international restaurant rankings. Spanish chefs, led by Ferran Adria of El Bulli restaurant, have created a market for kitchen instruments that would look at home in a laboratory: blast freezers, chrome griddles, water circulators. There's no need for a naked gas flame these days. ''I have used the technology but I haven't made it so removed that [diners] don't know what's going in [their] mouths,'' says Universal restaurant's Christine Manfield, who believes most patrons are unaware fine restaurants are cooking sous vide.

Beyond the city's adventurous top chefs, cooking in a plastic bag is still regarded with suspicion, according to Robert Erskine, who sells high-tech gadgets and equipment for Spanish company International Cooking. Erskine says they are not yet snapping up the thermostat, vacuum sealer and water circulator needed to cook sous vide. ''Chefs are still looking at it. They don't buy it,'' Erskine says. ''It's a coming thing.''

But Sydney's three-hatted chefs have been doing it for years. Tetsuya Wakuda of Tetsuya's says reading about the method inspired his renowned confit of ocean trout in 1987. At first, he used oil to create the air vacuum. It wasn't until the early 1990s that he had success with the new equipment. Fish expert and chef Greg Doyle says even bananas get the treatment in one of the desserts in his restaurant, Pier. At Marque, strawberries are cooked sous vide with sugar at 65 degrees for 40 minutes. Their grey carcasses are discarded and the remaining syrup is put back in a plastic bag with fresh strawberries and then vacuum sealed. The process forces the syrup into the fresh strawberry, creating hyper-real, translucent flesh.

Similarly, Best says, watermelons and cucumbers are given an exaggerated flavour so a diner might think: ''This is like the watermelon I used to know.'' The new technology has allowed food to be developed without pricey ingredients. Best says high-end restaurants are no longer distinguished by a menu of overtly luxurious ingredients such as truffle, foie gras and caviar. ''It's the intrinsic quality of every ingredient we focus on. Caviar is [just] slightly fishy eggs. It's the same with meat. If you look at the fillet, its only qualities are [its tenderness] but, really, it's not flavoursome and the texture can be a little mundane.''

Best uses tough cuts like brisket and short rib, cooks them for 18 hours at 65 degrees, chills them in an ice bath, returns them to a water bath for 40 minutes at 55 degrees and then sears the portion before it is put on the plate and served. The end product looks like a medium-rare steak but with much more flavour. ''This is a third-class braising cut turned into a first-class product through this technology,'' Best says. ''Traditionally, fillet was the cut that was only at the best restaurants … Now there's been a complete [reversal]. Why would we bother with fillet?'' At Quay, Peter Gilmore does similar things to a shoulder of lamb, traditionally another cheap cut, cooking it for 24 hours. Another beloved instrument is the Pacojet, which creates instant sorbets and ice-creams. There is no need to add sugar to stop the ice-crystalisation process, Best says. It enables him to put the humble pea at centre stage in a sorbet, with no other ingredients besides a little salt and pepper. Best calls it the ''peasant mentality'' of using everything. The same goes for fish. ''There's no waste from our kitchen.''

Apart from those plastic bags. Erskine estimates each of the top kitchens goes through 1000 bags a week. Chef Shannon Bennett of Melbourne's Vue de monde says the wastage is a problem: ''You feel there's a real trend that will start with this. It's so convenient and so healthy … The only area I would like to see improved is the vacuum-pack bags.'' There is something about this laboratory-like cooking that is a bit, well, frigid. Fans of Anthony Bourdain's Kitchen Confidential account, with all its heat, both allegorical and real, will not love what sous vide heralds: the cold kitchen. There are no aromas with sous vide. Everything is sealed into the food and saved for the plate.

It is now possible to set up without any exposed flame, thanks to the development of induction stoves, steam ovens, blenders that cook while they mix and water thermostats. Bennett does it at his new outlet, Cafe Vue at 401, Melbourne. The advent of sous vide has allowed chefs to prepare more before service starts, taking the stress out of the kitchen environment. In a traditional kitchen, ''people are trying to time things, putting them into the oven, tasting, saucing'', Best says. ''That's a super-heated and stressful environment and that's not conducive to quality.'' Manfield agrees: ''For me it's about efficient, calm cooking.'' For something so apparently cutting edge, sous vide has been around a long time. The method was developed in the 1970s in France for Pierre Troisgros, one of the fathers of nouvelle cuisine, to stop foie gras shrinking under heat. It has been applied heavily in industrial food preparation, thanks to the work of food scientist Bruno Goussault.

After initially working with hotel chains and airlines on low-heat cooking, Goussault's methods caught on with chefs such as Thomas Keller, who were becoming increasingly interested in the science of food. The Roux brothers, who revived French cuisine in England and mentored hundreds of chefs, are also credited with spreading the word. Dietmar Sawyere of Berowra Waters Inn has been using the technique since he worked as executive sous chef for Regent International Hotels in Hong Kong in the mid-1980s. ''Sous vide cooking started with a reheating method, then a lot of chefs around the world played around with it,'' he says.

Sawyere sees no reason to broadcast the method. ''One of the things I have noticed is chefs will put on the menu 'cooked sous vide' … I see it as an irrelevance. I wouldn't put 'cooked in a roasting pan' or 'baked in a baking tray'. It's a cooking method.'' By contrast, Quay restaurant's Peter Gilmore wears the method loud and proud because customers are curious, he says. ''There's no doubt, the face of cooking through sous vide has changed,'' Gilmore says.