In the bag

Now that food alchemist and chef Ferran Adria has created a successful synthesis between haute cuisine and industrial food-processing techniques at his exceptional restaurant in Spain, El Bulli, chefs everywhere are warming to sous-vide (French for 'under vacuum') cooking - ingredients vacuum-sealed in a plastic bag then cooked at low temperatures in a water bath (above) before being served.

Sous-vide is very different from the 'boil-in-a-bag' frozen meals the technique's description brings to mind.

Chef Bryan Nagao of D. Diamond, in Kowloon's Elements mall, has a vacuum-packing machine in his kitchen. 'I first came across the process in the Hyatt Regency Waikiki, [Hawaii] where I was working for a British chef doing French food,' Nagao says. 'We didn't use it for much - lamb shank and breast of chicken; that was it. After I came to Hong Kong, I consulted for Chez Moi. We bought a vacuum machine and did the moistest lobster with it, as well as squab and duck.'

Nagao finds the western technique compatible with the Japanese flavours and ingredients in his D. Diamond dishes. 'For the Japanese strip loin medallion, I portion the meat, vacuum it in with some caramelised vegetables for flavour and poach it in a water bath at 50 degrees Celsius for about 30 minutes. The meat is so tender, it's like cutting butter. Cooking vegetables sous-vide helps them retain their shape for presentation.

'You can buy vacuum machines and different-sized vacuum bags along Shanghai Street,' says Nagao. 'Make sure the width of the bag is less than that of the seal on the machine. Machines go for between HK$10,000 and HK$14,000. For cooking the vacuum-sealed parcels, you can invest in a thermal circulator [which keeps the water moving, for even cooking]. I don't use one; instead, I use a water bath in my Combi oven [a computerised oven that is equipped to cook with dry heat or steam]. If necessary, we stir the bath by hand.

'One thing to be aware of is the pressure setting on the vacuum. If you turn the dial too high for a piece of beef, you can suck some of the blood out - you want to avoid that.

'It is a time-consuming method. [Preparation] can take 30 minutes or longer. So I tend to use sous-vide more when I do a special tasting menu, so I have more control over the flow of the meal.'

Food cooked sous-vide has been known to retain higher nutritional value; the intensity of flavour and moisture are also unrivalled. But if you enjoy tasting, touching and smelling as you cook, this may not be your method of choice.