If your favorate French restaurant was not up to its usual standards last night, it may be because the chef wasn't there. He had exchanged his toque blanche for a pin-striped business suit. And except for a blue satin sash across his chest, he and seven fellow chefs were indistinguishable from the other guests elbowing their way to the buffet table at the Belgian Embassy.

"My god, it was a massacre," said one of the embassy waiters as he surveyed the decimated platters and the pate ground into the newly cleaned rug at the 6:30 to 8:30 p.m. reception honoring some of Washington's best practitioners of the art of French cooking.

There was Lion d'Or's Jean-Pierre Goyenvalle, fresh from vacation in Acapulco, and Bernad Binon, fresh from cooking 1,100 pounds of strip sirloin in his Mayflower Hotel kitchens for the White House state dinner Monday night, and the embassy's own chef, Ludo Ramaekers, fresh from his kitchen where he spent the entire day preparing the buffet (most of which has disappeared within the first hour).

It may have been the first time that Washington's cooking establishment had come face to face with Washington's perennial party-goers.

The chefs were the guests of honor, for a change, because they are contributing their services, each teaching a 2 1/2-hour cooking class at L'Academie de Cuisine during April for the benefit of the Homemakers Health Aide Service. The service gives inhome care to the ill and elderly who might otherwise have to be institutionalized.

The chefs had been rounded by their restaurant patrons, except for Ramaekers, who had been pressed into service by his boss, the Belgian ambassador's wife, Mrs. Willy Van Cauwenberg, who was honorary chairman of the benefit committee.

"Perhaps." a veteran party-goer observed, "the reason they are eating so much is because they paid $25 for it." That was Ramaeker's observation, too. Ramaekers took with good humor the "destruction" of the four kinds of pate, the filet of beef tartare and his artfully folded slices of country ham, through he sighed a bit when he said: "I prepared a lot more of platters than usual, but I like it better when they walk around and look first."

The guests, four deep at the table, interrupted their meal when Virginia Sen. and Mrs. John Warner walked in. Elizabeth Taylor Warner, who is on the benefit committee, agreed to pose with Phillipe Laurier, chef of the new pastry emporium, Palais de Friandises, and some of his petits fours. But then she confided to a reporter: "I always feel ridiculous posing over the marzipan."

Jane de Graff, socialite and committee member, didn't feel ridiculous at all, posing as a french maid in an abbreviated black uniform with black net stockings. "I've never had so much propositions in my whole life," she said.