Christmas eve in many homes lasts well into the early hours of the following day, when festivity gives way to the sober task of setting out presents or simply preparing for the emotional onslaught of Christmas itself. If a little fortitude is called for, pour a half-inch of cognac into a smallish snifter (rather than a fish bowl), warm it with your hands (not with a candle), smell it (do not thrust your nose into the snifter; cognac can be appreciated at a distance) and then sip it.

What you will discover is the ideal marriage of wood and alcohol, a smooth, off-dry, warm evocation of fruit, flowers, the autumn earth and other essences that hang tantalizingly beyond the edge of memory. Good cognacs are quite translucent -- the dark ones are usually heavy with caramelized sugar or added wood extract -- and if drunk sparingly will bring on a sense of generosity and well-being, inspire good conversation or ripe reflection, and leave you clearheaded in the morning.

Cognac is just distilled wine -- twice distilled, in fact. It comes from the region around the town of that name, one of the most famous in France and, some say, the most universally known of all French words. Cognac is just one of the generic class of brandy, derived from a Dutch word meaning "burned wine," but it is the brandy, made from grapes grown in the chalky soils of Charente and Charente Maritime. Brandies are made all over the world, but in Cognac they reach perfection in the distilling and aging in vast numbers of Limousin and Troncais casks, some of them 200 years old.

All cognac is a blend. Much of it is made on the premises of the small growers. The grapes used are St. Emilion, folle blanche and colombard; an acidic white wine is made from them. It is twice boiled and evaporated in old-fashioned "stills" with an onion-shaped chapiteau and the final product is delivered to the big houses in Cognac and neighboring Jarnac. They also distill much of their own cognac. Various years are blended according to age and quality; consequently, most cognacs do not bear vintage dates. Cognac ceases to improve in cask after about half a century; once bottled, it does not age further or change appreciably in character. After the bottle is opened, slow oxidation will take place.

Cognac labels are confusing. Grande Champagne does not mean that the cognac is related to sparkling wine of the same name, but that it comes from the best region in Cognac, with soils similar to those in Champagne. Petite Champagne is one step down and slightly lighter. A blend of the two is called Fine Champagne, or Grand Fine Champagne. Three-star cognac, also known as V.S. (Very Special), is supposedly from five to nine years old; V.S.O.P. (Very Superior Old Pale) from 12 to 20 years. The age of cognac required by the French government is considerably less. V.V.S.O.P., Napoleon, X.O., Gran Reserve, Vieux and Vieille Reserve are older blends, of better quality and higher price.

Even the more reasonably priced cognacs are expensive by most standards. I can recommend three in ascending order of cost, quality and style: Hine V.S.O.P. ($20); Martel V.S.O.P. ($21.50), and Delamain's Pale and Dry ($26.50), lighter than the other two but with rare finesse and great staying power. One of the best cognacs I have tasted is Delamain's unblended 1930, made available in a trade tasting last year. Some of it may be found in Delamain's Tres Venerable, for the equally venerable price of $75 a bottle.