The drinker | saké

You've ordered your meal and the waiter asks what you'd like to drink. You say: "Wine, please." The waiter writes down the order. Does that sound plausible? Of course not. But substitute the word saké for wine and you're reproducing an exchange that takes place daily in Japanese restaurants. Sakés vary gigantically in quality and style, yet most drinkers still regard them as an undifferentiated commodity. And most restaurants sell just a single brand of basic (that's a euphemism) quality.

You've ordered your meal and the waiter asks what you'd like to drink. You say: "Wine, please." The waiter writes down the order. Does that sound plausible? Of course not. But substitute the word saké for wine and you're reproducing an exchange that takes place daily in Japanese restaurants. Sakés vary gigantically in quality and style, yet most drinkers still regard them as an undifferentiated commodity. And most restaurants sell just a single brand of basic (that's a euphemism) quality.

Keen to get a sense of the full range, I thought immediately of Nobu, London W1. With such innovative food, and such frightening prices, I figured they must do saké seriously. I made a date with Stephane Guicheteau, the restaurant's drinks manager and a famed saké proselytizer. What more could I need?

Well, I could need some understanding of how the drink is made. This came from www.esake.com, a fantastically informative website run by a fanatically saké-mad individual named John Gauntner: start with highest-quality short-grain rice and mill (polish) it to remove the grain's outer layers. How much you remove depends on how expensive your saké is going to be; the loss ranges from 30 to around 65 per cent. After milling you wash the rice, soak it, and steam it in big vats.

In the next step, "the heart of the entire brewing process", Aspergillus oryzae (koji-kin) is sprinkled on the rice. This is a mould that breaks down rice starch into fermentable sugar and the mixture is left for a couple of days with frequent stirring. Not all the rice goes through this process, but the fraction that does - called koji - gives the drink much of its character.

For brewing, a yeast starter is made from koji, plain rice, water and yeast cells. This takes a couple of weeks. The starter then goes into a tank and rice, koji and water are added in three stages over four days. Fermentation takes 18 to 32 days, and a little extra alcohol is added to some sakés. After final treatment, the saké is usually aged and water is added to bring its alcohol content down from around 20 per cent to 16 per cent or so.

And so to Nobu, where M Guicheteau is sitting with six open bottles. All come from the small, privately owned Hokusetsu brewery, whose products are sold (outside Japan) only to the Nobu restaurants. Reversing the usual tasting modus operandi, we're starting with the most expensive. "These are finer and more delicate," says M Guicheteau. They are drunk chilled, contrary to the practice in most restaurants (where warmth conceals inferior quality).

As we taste, enormous differences become apparent. Some sakés taste strongly of koji (pleasant fungal-ness reminiscent of ceps). Some are flowery, or have a powerful scent of banana, others of lychee. Some are noticeably alcoholic in impact even though their ABV is no higher than others. Dryness ranges from bone-type to semi-sweet.

I wish I could report that I liked the cheapest saké best. It ain't so. The more rice you remove in milling, the better the brew is. And the more expensive. Ginjo saké has had at least 40 per cent of the grain removed, Dai-ginjo at least 50 per cent. These varieties put the others deeply in the shade. At Nobu, the best stuff on the main list costs from £23 for a 300ml bamboo "carafe". The "fine-wine" saké list, sold only in 720ml bottles and therefore untasted by me, is £55-120. Top choices: Ongakushu, aged for 10 years with music playing in the background (£29/300ml), or Junmai Dai-Ginjo (£26/300ml).