YOUR CHRISTMAS stocking is being filled right now. Truckloads of cheeses, planeloads of caviar and smoked salmon, a couple hundred kinds of mustard and even more kinds of jam have been piling up at the Washington Convention Center for the 29th annual Fancy Food and Confection Show--held here for the first time and open only to the trade, not to the public--today through Wednesday.

"It's a living catalog," says Vincent Dole, member of the show committee ("I'm the local warm body," he says of his title). Held twice a year in various cities but every other year in New York, the now-International Fancy Food and Confection Show hits its zenith in the summer showing; it is where retailers, from small shops to supermarket chains, see an array of fancy foods from around the world and start their Christmas shopping. They look, they taste, they buy. This year, the first time the show is called International, 21 countries will have booths and foods will come from 41 countries. Thus Holland's newest cheese may soon appear on your neighborhood shelves.

Jams and mustards vie for the proliferation award, though as Dole reminded, "Mustard is limited by mustard seed." There will be jams from old family recipes and from fruits unheard of outside their regions. "There is going to be a lot of pasta, for sure," Dole added. And all the caviar people from around the world. "This is," said Dole, "the caviar, pa te' and cheese show in the U.S." Olive oils are big this year, and very fancy chocolates (among them chocolate computers and chocolate typewriters). Not only foods are coming, but the people behind them: Carl English, the California fireman with his Firehouse Bar-B-Q Sauce, Giorgio DeLuca of New York's much-imitated Dean and DeLuca store, Dino de Laurentiis of cinema and DDL Foodshow fame, Prince Albert of Belgium and armadas of British representatives who are about to launch a giant sales campaign following that country's American Food Marketing Report, the contents of which will be revealed during the show.

The British are providing the theme for the show and the grand banquet for 1,000 guests tonight at the Shoreham, not to mention double-decker buses to transport the estimated 15,000 out-of-town visitors from their hotels to the convention center each day.

The issue to be discussed formally tomorrow and informally throughout the show will be the role of supermarkets in marketing fancy foods, since they are rapidly increasing their selections of specialty foods and thus challenging the small specialty shops that have been the mainstay of the business.

The question to be asked on Wednesday, suggested Dole, is, "What's going to happen at the end of the show to all that stuff?" The wheels of cheese, the sides of salmon, the cases of mustard--in Dole's experience the last day the staffs, especially those in foreign booths who are neither capable nor interested in shipping home leftover cheese, become very generous with their samples. Said Dole, from the freebies being handed out the last day, "You can stock a store."

The tomatoes are late, the corn is slow but one thing that is coming up early this year is Taste of the Town. This year's dates are July 9-10, rather than the usual late July, and for the first time Washington's Taste will be followed the next weekend by Baltimore's companion show, in case you find it addictive.

What's new in this 4th annual restaurant festival and mass tasting? First, it's at the new convention center, which means twice the floor space and better metro access (Metro will be giving two 25-cent tasting tickets to visitors who show their farecard). Second, there will be samples from 101 restaurants (last year had 74) including Bacchus (hummos and baba ghanouj), China Coral (shrimp crepes and crispy fish roll), Gary's (fried calamari), Tunnecliffe's (mesquite-grilled chicken), Joplin's (seafood gumbo) and My Brother and Me (swordfish salad and seafood brochette). And Famous Amos himself will show up to promote Louis Sherry's new Famous Amos ice cream. The hours are also expanded, Saturday 11 a.m. to 8 p.m., Sunday 11 a.m. to 6 p.m.

"Part of the event is being crowded," says Taste planner Sandra Butler Whyte; to beat the crowds, she suggests, decide ahead what you want to eat and aim for those lines. The most popular foods have in previous years been the Sheraton Washington's fruit fantasia, O'Brien's ribs, Joe and Mo's potato pancakes and seafoods--of which this year there will be plenty. Admission is $4 to $6, depending whether you buy in advance (from 17 locations) or at the door, and whether with or without a coupon (available all over town or call 548-4034 to find one); children 12 to 18 are $3, under that age free. Also new this year is a VIP lounge with complementary drinks, tickets for which cost $25. As for the food, "tastes" will cost 50 cents to $1.75.

Vanilla has joined the mainstream in main courses, or at least in seafood courses. It all started in Paris, where Alain Senderens of L'Archestrate restaurant introduced lobster to vanilla; it doesn't add sweetness, he explained, but picks up on the natural sweetness of the lobster. We saw it next in New York at Senderens' Maurice restaurant in the Parker Meridien Hotel, then in Washington at La Reserve in the Embassy Row Hotel. Next it is slated for the Golden Anniversary benefit dinner for the Easter Seal Society July 7. The Sheraton Washington's catering director, Gary Budge, has designed a menu that starts with lobster in vanilla sauce carried about as far as it could go: avocado crepe filled with lobster and crawfish e'toufe'e served with vanilla saffron sauce. The menu goes on to duck with ginger, veal wellington and chicken breast with lamb and feta, accompanied by a magician's performance. If you've got to taste it to believe it you can do so for a tax-deductable $100 a person by calling 232-2342.

It has been rumored that music enthusiasts have starved in their devotion to hearing Wagner's Ring Cycle uninterrupted. Chamber music lovers are much more light-hearted, so The Barns at Wolf Trap is catering to them with Dessert Concerts, the last of which is tomorrow night, June 27, at 8 p.m. The music will be Bartok, Schumann and 1983 Pulitzer Prize winner Ellen Taaffe Zwilich. The desserts will be French fruit tarts, ice cream sundaes, Triple High Apple Pie and Amaretti Torti, to nibble before, at intermission and after the concert. Tickets are $12; call 938-2404 Monday between noon and 6 p.m. And if the number is busy, you can turn on the stereo and make the Amaretti Torti at home. Here is the recipe: AMARETTI TORTI (Makes 9-inch cake) 10 Amaretti biscuits (or 40 small Amaretti) 4 ounces semisweet chocolate 1 tablespoon water 1 cup (2 sticks) sweet butter 1 cup sugar 5 eggs, separated 1/2 cup flour Confectioners' sugar for topping

Line bottom of a 9-inch cake pan with waxed paper. Butter and flour paper. Pulverize cookies in a blender or food processor until they are fine crumbs. They should yield about 1/3 cup. Melt chocolate with the tablespoon of water until smooth when stirred. Let cool.

Cream butter well; add sugar and cream until fluffy. Beat in egg yolks one at a time. Continue beating until light and fluffy, about 5 minutes. Add flour and cookies alternately. Fold in chocolate. Beat egg whites until stiff. Fold into batter.

Turn into prepared pan. Bake at 350 degrees for 40 to 45 minutes until a knife inserted in the center comes out clean. Cool 10 minutes. Invert on a rack and peel off waxed paper. When cool, dust with confectioners' sugar.

Garnishes can range from anything with chocolate to strawberries, whipped cream or ice cream.