We came to sample dessert wines, but mostly we came for the 'Quem. That's enoese for Ch.ateau d'Yquem, the ultimate essence of Sauternes, that region of Bordeaux producing lush, sweet, golden wines. This was a 1977, a mite young, impregnated with Botrytis, the mold that attacks mature grapes and releases moisture while preserving the sugar content. The French call it "pourriture noble"--the noble rot. Supposedly discovered by chance when moldy grapes were ordered harvested and processed by a recalcitant estate owner, it became the basis of Sauterne's one premier grand cru; it is used in other sweet wines as well. The grapes must be selectively picked by hand over a period of weeks, making the product excessively dear. The first assault of Botrytis upon the taste buds, if the wine is well-made, is unforgettable.

The tasting was held in the bright cellar of Wide World of Wines, in Spring Valley, the walls hung with promotional maps of the world's great wine regions. Tasters included a lawyer, a journalist, four professionals and half a dozen wine enthusiasts of varying degrees of expertise. One kept a bag of air- popped corn nearby, to cleanse the palate; others contented themselves with the cashews and macadamia nuts, banana bread, tarts, melon balls and sliced peaches. No receptacles here for spitting out (expensive) Botrytis.

The wines, all chilled, were led by a 1981 Ballard Canyon Johannisburg Riesling Reserve, spritzy and not too sweet, with a clean, apple taste. At $5 for a half-bottle it represented the best compromise between price and quality, but unfortunately the supply in infinitesimal. The 1977 Cispiano Vin Santo ($9.79 for a standard bottle), made with muscat grapes, proved a little harsh for on the palate, but good for dipping cookies. The 1980 Sutter Home Muscat Amabile was lighter, with a trace of licorice, perfect for cr.epes or most light desserts. You might also pour it over ripe sliced apples and chill the result for an hour in the refrigerator. The 1976 Erbacher Michelmark Trockenbeernauslese--that means the latest-picked, sweetest berry-like grapes of the Rheingau--had a deep, golden color, a wonderful nose, an almost syrupy consistency, and a full, spicy flavor. You get all that for $33.20, in a half- bottle. The 1981 Austin Cellars Sauvignon Blanc, all Botrytis grape, had a touch of grassiness and a long, sweet aftertaste. Some detected apricot; others a smokiness that warred with the sugar. It would be delectable finish for most meals, but is expensive at $12.50 the half-bottle.

At the conclusion of the tasting the speaker made a pitch for "corporate wine gifts" that lacked finesse; otherwise the experience was pleasurable and enlightening. Now, if you have no interest in dessert wines or the noble rot, and are trying to expand your knowledge of wine with limited resources, was this tasting worth the $25 fee? Probably not. However, the only way to learn wine, other than reading about it, is to drink and discuss it with those who know as much or more than you. A great deal of general knowledge is imparted by participants, and by local authorities and vinous stars from abroad who inevitably pass through Washington. So pick your grape and save your money; I'll list some up-coming tastings next week.

And . . . oh, yes, the 'Quem. It was adjudged satisfyingly complex, but too "hot"--meaning alcoholic, and immature, a mere penultimate dessert experience. But then what do you expect for only $55 a bottle?