NOT EXACTLY prime Broadway material, these 32 Ridgewells waiters. Never mind. They've got exactly 28 minutes to learn how to strut, hold two mousse-like desserts aloft and grin, pretty much foolishly, to "One" from the musical "A Chorus Line."

"Okay, you got it?" says Dennis Cory, who is choreographing this little dessert number for the annual Wolf Trap Ball. Some of the waiters look like they might, but others seem addled.

"I feel like the Galloping Gourmet," says one.

"Strut," says Cory. They strut. "Stand real straight and smile while you do it," Cory instructs. "Drag your foot behind you like this." He drags. "You've got to come out even," he grumps, surveying the two wiggling lines ot tuxedos and white serving gloves. "This is terrible. Go back."

By dessert time, things have improved. Most of the waiters can do respectable struts; the rest have mastered reasonable fakes. The lights dim, the music begins and two phalanxes parade on the Wolf Trap stage with gourmet fodder called Paris Brest in their palms. The guests, sluggish from too much cordon bleu and partly chit chat revive.

"I've never done this before," says Chris Letelier, who leads the right line of waiter/strutters. But he is blase, nonchalant. After all, when you work for a caterer like Ridgewells, strutting with mousses to music is just part of the job.

Ridgewells is the number one society caterer in a party boom town that may be, per capita, the number one reception-thrower in America. It is a company that handles close to 8,000 parties a year, sometimes up to 60 a day, from reuben sandwiches at the White House to canteloupe cannons at the Pentagon to sirloin of beef au piovre to 50 good friends of Mideast negotiator Robert Strauss.

Ridgewells will deliver 3,000 pink napkins, 500 peach pies or a solitary mocha eclair. ("A lot of people will pay us $10 to have a Ridgewells truck sit in their driveway," says Jeff Ellis, the president.) Or they'll whisk a ham, and fast, to a frantic Rose Marie Bogley who's got 75 coming to dinner -- and nothing to feed them -- in Middleburg horse country.

"Rose Marie will call and say," says Bruce Ellis, Jeff's twin and Ridgewells vice president, "'Oh, Brrruce, Jeiffff [this is delivered in a Scarlett O'Hara come-hither tone], can you just do me a little ham or a roast beef?'" Always in the last minute, between 50 other parties, of course. "But she's a super-duper customer," says Bruce. "So we go ahead and do it."

Other all-star customers are the John Warners, the Kimball Firestones and seemingly every charity ball, government agency, art gallery, department store, lobby group, law firm and political candidate in town. Garfinckel's. Fulbright and Jaworski. The FCC, CIA and FBI. The National Portrait Gallery. The Treasury. HUD. The Corcoran Ball. And "assistance," either in terms of additional party food or rented party equipment to Henry Kissinger, Ethel Kennedy and Averell Harriman.

"I wouldn't use anyone else," says veteran customer, socialite Melody Gilsey. "We understand each other."

Not everyone raves.

"Those guys over there will do all they can to stab you," says a major competitor in town. "They're arrogant."

It is a complaint echoed by other competitors as well, many of whom also mutter words like "snobby" and "expensive" when describing Ridgewells.

And some describe the food served as below par for its high price. "It's never been fantastic," sayd another Washington caterer, specifically mentioning the Ridgewells' chicken tetrazzini featured at a recent party which "didn't remotely resemble tetrazzini." What it did resemble, he won't say.

Still others say that when a company grows as fast as Ridgewells, problems grow too. Labor, for instance. "The market is not what it should be," says Bill Seltzer, president of Columbia Catering. "You can't get the numbers of qualified people. When you need 100 waiters, you get 30 waiters and 70 bodies."

Counters Ridgewells' Jeff Ellis: "I have absolutely the best help in Washington." And on tetrazzine: "We wouldn't have had the growth that we've had if our food was bad." And the snobbery? "We don't do $3.95 weddings. That doesn't mean we're snobs."

But despite the complaints and four main competitors -- Avignone Freres, Braun's, B&B and Columbia -- Ridgewells stays on top of a Washington catering industry estimated to gross $20 million annually.

In fact, Ridgewells does so much party catering these days that the twins find themselves playing party arbiters. A recurring scene: "Jeff," says a hostess into the phone, "I'm thinking of having a few hundred next week. What's a good night?"

A good night is one relatively clear of pencil scratches in the Ridgewells date book. Thus, the clever hostess can avoid competition from big-draw and big-name events like balls and state dinners.

"We're a clearinghouse for all sorts of people," says Jeff. "Even people who are having their own parties will call us and ask what's happening on a certain date."

But never, ever will the twins talk. Not about your party, your guests, the chips in the china, the woolies under the couch, the little scene they caught in the pantry. Secrets, forever.

Or sort of forever.The twins, probably at this very moment, are storing yet another juicy party fact in their brains. It'll be scrawled on loose leaf paper later, stashed in a small office safe a little later and compiled into a book about Washington catering even later -- "one day when we're old and retired and bored," promises Bruce. He says it'll be nice, not nasty.

Friday, Sept. 7. Nothing much significant about the date except that it's a good three days into Washington's fall social season. Which means parties, receptions, barbecues, dinners, picnics, lunches, brunches . . .

And Ridgewells is ready. At the Bethesda headquarters, the troops line up at dawn.

6 a.m.: Mounds of swiss cheese spring up on silver platters. Slews of eggs fall in slices. Hundreds of shish kebobs are born on skewers. Piles and piles of strawberries grow steadily on a giant chopping block. A mushroom quiche cools, the carrot puree flows, or squishes, actually, into 400 cucumber boats.

This tornado of kitchen activity is frightening to anyone accustomed to walking slowly in range of a civilized hour with a placid cup of coffee, perhaps.

In this kitchen, forget it. Morning coffee is a mass affair, brewed in a giant silver urn and pretty much inhaled by 25 frenetic staffers who have 22 parties to cook for and not nearly enough hours to do it.

The annual Wolf Trap Ball is one of the big ones today: 380 arts and party-conscious Virginia socialites eating (in order) sweet potato, eggplant and raw broccoli tempura, chicken cordon bleu, sauce supreme, white rice, cucumber boats with carrot puree and nutmeg, french bread, bibb lettuce salad, puff pastry, Paris Brest and demitasse. The bill? Close to $8,000. s

Other parties, as they exist on the yellow order sheets tacked to the kitchen bulletin board, include: a reception for the American Academy of Pediatrics, a paella party for 40 in Chevy Chase, a bon voyage party for "Larry and Kay" that needs a shamrock cake, receptions at AT&T, the Riggs National Bank and Intelstat, a dinner at the National War College featuring boneless veal and another dinner at Robert Strauss' home featuring steak and other delicacies, which, to add to the general bedlam, Strauss ends up canceling.

"Hello, everybody." This is a bright 8:20 a.m. chirp from Jeff Ellis, who wears three immaculate pieces of navy pin stripe. He's been in his office since 7:30, but he's just now making his first tour of the kitchen.

Jeff, like Bruce, is the kind of boy you'd take home to mother. He is lean, rosy-cheeked, charming and polite. Hostesses and society ball chairwomen think he's divine. "They're both adorable," says Rose Marie Bogley. "I think everybody's in love with them."

The pair head a Washington institution created in 1928 by a butler and chef at the French Embassy. The butler was Charlie Ridgewell and the cook was his bride, Margaret.

Back in those days, catering meant not mammoth chicken liver molds but delicate finger sandwiches for tea. A tender baby tomato or two. And lots of sherry. From there, catering grew with the embassies, then with the government. In 1946, Ridgewell sold the company to son-in-law Clarence Ellis, and today, Ellis' 35-year-old sons head a business that caters to presidents, has 400 employes during peak months and grosses $2 million to $6 million annually. Those dollar figures are competitors' guesses; the twins think it's a little, well, common to talk money.

But they'll talk volume with little prodding, claiming that in the last five years their business has easily doubled. They say they're not sure why, but think it's got to do with the city growing larger and more cosmopolitan. T"When the Kennedy Center was built, that might have been the springboard," says Bruce. "That's the time when we saw a lot of new names in town."

"Washington is booming," agrees Jeff, ticking off a list of corporations, banks, culture groups and social clubs he caters to. "There's only one way you can put them all together," he adds, meaning around a well-laden buffet table. "You sure can't put them in a hot tub."

9:30 a.m.: Four 10-pound salmon sprout cucumber scales. Thousands of peas drip into strainers. Baby potatoes lie scrubbed and bisected, waiting for caviar. Fifty pounds of white icing swirl around two over-sized beaters; oil sizzles, pastry cools and on the sidelines, pastry chef Vijay Sharmas clears the boards for a mid-morning battle.

His task is the creation, before lunch, of 45 Paris Brests. From the bottom, the layers: almond cake, whipped cream, chocolate mousse, whipped cream again, more cake, strawberries, strawberry glaze and powdered sugar. It is treachery, sheer treachery, for a dieter.

"Bring the strawberries and powdered sugar," Sharmas cries to an assistant.

The pastry chef is like a surgeon in overdrive, dashing frantically from mousse to strawberries to whipped cream and back.

Suddenly, a finger pokes into the 25-pound tub of mousse, followed by an "ummmm." Both belong to Bruce Ellis, who like almost everybody else at Ridgewells, is not fat.

"Gotta sample a little bit of everything," says Ellis, who says executive pressure and tennis eat at the flab. "This business will keep you skinny because you run around so much. And you don't eat right. A lot of times on the way home, we'll stop at Roy rogers."

Twenty-five feet from the mousse is the person responsible for it all. This is Maurice Dufour, executive chef, formerly of the Jockey Club, formerly of a neat little restaurant in the south of France, formerly of Puteaux, a Paris suburb he likens to Alexandria.

He is the French version of the Ellises, and comes with charm, crisp white jacket, rosy cheeks, a lilting accent. And also a phone in his ear, used to place the endless orders of mushrooms, peppers, sausage, chicken, lobster . . .

Not too much lobster lately, though. "We don't sell seafood like we used to," says Dufour, "because seafood is very expensive. When you think that one gallon of lobster newburg costs over $100, well, people stay away from it."

So here's the "in" Washington party food these days:

Veal. "Nobody knew much about it before," says Dufour.

Chicken, any way you want it -- roasted, broiled, fruited, sauteed, breaded, stuffed, stewed. Any way, really, except breathing.

Beef tenderloin. "Always popular," says the chef.

And escargot and steak tartare, two current rages. "Five years ago, nobody wanted to touch raw meat," says Maurice. "Now all sorts of people ask for it."

Confirms Jim Schwab, a Ridgewells salesman: "When I first got into catering, the thought of steak tartare was abhorrent. Or at least it was in Pennsylvania, where I came from. If you asked for steak tartare there, they'd tar and feather you and run you out of town. But now, I love to eat it on toast points."

Here's the "out" food:

Pork. "People are always afraid to use it," says Dufour. Liver and onions. Rabbit. And venison. "Wild meat people aren't crazy about," says the chef.

A subcategory of "out" food is the food disaster, which Ridgewells lives in moderate fear of. There are as many legends that start "Remember the time when the sauce curdled/dessert almost bombed/table collapsed" as there are, hmmm, calories in the mousse. Or peas in the strainer.

Dufour has his own favorite near-disaster story. This one takes place at the Chevy Chase Women's Club, one very hot summer Sunday.

"Twenty gallons of chicken turned bad, just like that," he recalls. "I couldn't believe it. But Bruce and Jeff were there, so we all went shopping. Then we came back here and fried it up and got it to the party five minutes before they started serving it. That scared the hell out of me."

Noon: lunchtime at Ridgewell's. The menu is paella, tossed salad, broiled dolphin and Coca-Cola. The kitchen crew eats at two tables in the middle of the strawberries and quiche that have been shoved aside for the moment. The Ellises and the upstairs salespeople eat in a small dining room off the main offices.

The Ellis brothers spend the break telling more Ridgewells lore. The lady and the salmon story, for instance.

"The salmon we sent this woman was definitely salmon," says Bruce, "but during that time of year they spawn and their jaws come up and you see their teeth and their color's no good. They just look uglier than hell.

"Well, she said her guests thought it wasn't salmon. Now I could have said, 'That's salmon, and you pay for it,' but that's not how my grandfather and father conducted business." He sighs, explaining he took $100 off the price of the fish, then says he wishes he could produce his own. "The name of the game is self-sufficiency," he says. "Now if I could raise cattle in this town . . ."

5 p.m.: The kitchen is now sterile and serene, except for the pastry chef who's still icing cakes. Out by the loading dock, Jim Schwab, the salesman, checks the list of food going to Wolf Trap in the big purple truck. Four gallons of tempura butter, 400 sweet potato pieces, 300 broccoli spears, 420 chicken breasts, 400 cucumber boats, 80 loaves of french bread, 430 puff pastries, 45 Paris Brests, 20 lemons . . .

This is the third Ridgewells truck to head for Wolf Trap today. The first two carried tables, chairs, silverware, napkins, glasses, plates and on and on and on.

Schwab climbs down into the driver's seat and heads for the Beltway. He's asked about the ferocious purple that all Ridgewells trucks are painted. h

"The color?" he responds. "Well, it's not what you'd call a pastel. Maybe hot purple? Or grape? Yeah, it's pretty close to grape. Sort of looks like a giant grape popsicle. Kind of Pavlovian, in a way. I think people sort of salivate when they see it."

Schwab is full of stories, too. He likes the recurring one about the hungry vegetarians.

"When you're having a French service dinner, the meat will be in the middle and you'll have it flanked by broccoli or carrots. If somebody's a vegetarian, you can have your platter wiped out and the meat gets to look lonely, awfully lonely, just sitting there by itself.The people say, "Gee, you couldn't afford too much for this party, could you? Sort of skimpy.'"

8p.m.: A cook readies a wok at the hors d'ouevres table. Sauce supreme bubbles on a portable stove set up in a behind-the-scenes, makeshift kitchen. Eric Waltenbaugh, the Ridgewells coordinator in charge of the benefit dinner on the Filene Center stage, checks place settings at 39 tables. They're covered with brown and white cloth and champagne buckets. Quickly, 32 waiters scramble to their places.

And then the guests, mostly Virginia suburbanites sprinkled with an occasional ambassador and one cabinet member, arrive. Treasury Secretary G. William Miller heads straight for the wok. "This is very good," he says, deftly handling chopsticks to gobble the broccoli tempura. "I used to live in China."

Midnight: The evening's carcasses lie strewn about the makeshift kitchen. Most are half-gnawed bread loaves, empty cucumber boats, Paris Brest remains. The kitchen crew garbage-bags most of it, bustling with the same frenzy as did the Ridgewells morning crew 18 hours earlier.

Jeff Ellis has been around most of the evening, watching over things, poking a finger here and there, hobnobbing with guests who are customers on other nights.

But now he grabs a gin and tonic, climbs into his station wagon, and rolls down the sunroof to expose a rectangle of September stars. He lights a cigarette, then heads for home. "Crazy business, catering," he says.