THE JEWISH high holidays last year fell right in the middle of the T Napa Valley grape harvest, so Hagafen, Napa Valley's first kosher winery, had to sit idle. It nevertheless managed to produce 1,200 cases of its Johannisberg Riesling, made from grapes bought in the Carneros Creek district of Napa Valley, in time for Passover this year. Last year, its first year of production, its total was 300 cases.

A kosher winery, explained Ernie Weir, one of Hagafen's three partners, has all the problems of a winery--plus all those of being kosher. It can't use gelatin, casein or isinglass for clarifying the wine, since those are of nonkosher animal origin. Even when it clarifies with egg whites, the winery must be careful to use only eggs with no blood spots. All the equipment must be koshered with boiling water and live steam, then left to rest for 24 hours before it is used, said Weir. And only Jews who are observant may touch the wine from the grape-juice stage through the bottling.

Hagafen wines are being made, said Weir, by "three nice Jewish boys" who met at UCLA and worked in Napa Valley. "We're not very observant," he further described the trio, "but we identify." And, of course, they like good wine, whether everyday or for Passover.

They came to a point at the Seder, he explained, when "there wasn't a decent wine to serve." So they decided to make their own kosher wine for Passover, aiming for a high quality varietal. "We couldn't figure out why it hadn't been done," added Weir. "There's no reason kosher wine can't be good wine."

As with many another good idea, this one's time seems to have come. Other kosher wineries in America have begun to upgrade their offerings of dry kosher wines, emphasizing varietals; and Kedem is increasingly importing European kosher wines.

Hagafen's wine already has been served at the White House, at a dinner for Israeli Prime Minister Menachim Begin; it was the first time the White House had served him non-Israeli wine. And last year's production was readily consumed in California and Chicago with none left for the East Coast market.

The 1981 vintage (also labeled with the Hebraic year, 5742) has just been released for the Passover holidays, and Morris Miller Liquors has stocked 15 cases. The bad news is that the price is high--$8.49--and several of us who tasted this year's offering found the aroma off and, after some initial pleasant riesling flavor, a finish of underripe grapes. So this infant winery still has a way to go; in the future it hopes to add chardonnay and cabernet sauvignon to its line.

Even for one week a year, sponge cake and fried matzo can become tiresome as the sole Passover treats, so a new Passover recipe is as welcome as the first crocus. In anticipation of the holiday, therefore, Passover cooking classes are being taught at the Jewish Community Center, 6125 Montrose Rd., Rockville, next Tuesday from 7:30 to 9:30 p.m., and at Williams-Sonoma store in Mazza Gallerie tomorrow afternoon at 1 p.m. The Jewish Community Center class will be taught by Bernice Kaufman; the fee is $10 for members, $15 for nonmembers. Call 881-0100 for more information. The Williams-Sonoma class will be conducted by Joan Nathan Gerson, author of "Jewish Holiday Kitchen"; admission is free.

Tea and sesame--or currants or mace--are what our 18th-century ancestors consumed on their afternoon breaks, for then there was no vanilla to flavor cakes, no chocolate-chip cookie vendor on the street corner, no vending-machine bag of corn chips. But you can find this out for yourself next Sunday (March 28) or April 4, when Alexandria's historic Carlyle House, 121 N. Fairfax Street, serves tea--four kinds--and Queen's Cake, Biscuit Cake, whatever tea cakes were popular in Colonial Virginia, made by the staff from 18th-century recipes, served by costumed docents and accompanied by period music. The star of the spread is said to be the staff's special Sally Lunn bread. Tea service will be 2 to 4 p.m.; admission is $3 for adults, $2 for ages 6 to 17, $2.50 for senior citizens. For more information call 549-2997.

The lobbyists are gearing up, the press releases are going out, an act of Congress is being demanded. All to name the cherry our national fruit, an effort by the cherry growers, processors and others in the industry as reported in their newsletter, "Cherry Life." The red stripes on the flag are being evoked in its behalf. Cherry blossoms--those fruitless District tourist trees--are having their name taken in vain. Even cherrystone clams and cherry tomatoes are being enlisted as support for the endeavor. Ah, but what would it imply for our country to have an official fruit of such short season? And what about the nutritionists' darling, the cantaloupe? Or the historic-frontier fruit, the apple? Isn't it strawberry shortcake one eats on the Fourth of July? Can one ignore the fashionable kiwi? The ice-cream-sundae banana? Frozen orange juice? And if fruit is destiny, the wine grape is certainly ours.

The bake sale has gone electronic. From tomorrow through Thursday WMAL radio is auctioning off 43 cakes to benefit the D.C. Society for Crippled Children. These are no ordinary cakes. Or at least they are cakes made by no ordinary bakers. A high price is predicted, for instance, for the cake baked by Jeanne Dixon. Ted Koppel's and J. C. Hayward's cakes should make news. The budget has not been revealed for Mayor Marion Barry's cake, nor has anyone guessed whether it will be any less controversial than Tip O'Neill's or Barry Goldwater's. Angela Buchanan, the U.S. Treasurer, is baking hers in the shape of a dollar bill, so it is bound to disappear fast. If you were going to actually eat it, you might want to bid on the cake by Le Lion d'Or's Jean-Pierre Goyenvalle, but if you are looking for a conversation piece for your coffee table, you might also take a chance on the culinary skills of Marvin Hamlisch, Barbara Bush or Howard Baker.