<i> VIVE LES CHANGES</i>

When a newly celebrated chef in this country leaves the employ of others and opens his own restaurant for the first time, it’s rarely a small and simple place. Stars-in-the-making around here want a heavenly environment--their cosmos ready-made; the scale must automatically be large, the design impeccable, the trappings opulent. On the restaurant fast-track, modesty is a sucker bet.

Things are a bit different in France. There, it is not at all uncommon for a promising young cuisinier , setting off on his own after making a reputation in somebody else’s kitchen, to start out with something low-key, tiny, inexpensive to maintain. Then, and there, said chef will build a following--and hone his skills. The fancy stuff will come later. But come it inevitably does, if the chef turns out to be indeed a talent, indeed celestial in his abilities.

Two of the best newer restaurants in Paris--Guy Savoy and L’Ambroisie (each of which, speaking of the cosmos, rates a pair of stars in the Guide Michelin)--have in recent months followed exactly that path, moving from their original undersized and underdecorated premises to splendid new quarters in which the splendid food they serve has found at last the framework it deserves.

Guy Savoy first came to the attention of the Parisian dining public as chef at the legendary Claude Verger’s La Barriere de Clichy in the 17th arrondissement . He opened his own place not far away, on the rue Duret in the 16th, about eight years ago. Michelin quickly gave him his first star--and then unaccountably dragged their feet about the second for five years while Savoy cooked rings around half the big-deal chefs in town with his highly refined, exquisitely controlled post- nouvelle cuisine.

The restaurant on the rue Duret was warm and not unattractive, but it was a bit too homey for such fancy-dress cooking. At least four years ago, Savoy decided that he wanted to move--and his subsequent unsuccessful search for an appropriate new location became almost a joke in French gastronomic circles.

Savoy got lucky earlier this year, though. Gilbert and Maguy Le Coze, proprietors of the two-star Le Bernadin seafood restaurant, had opened a branch office in New York--and liked the city so much that they decided to quit Paris altogether. Savoy was able to take over their attractive and well-placed site in the 17th arrondissement and turn it into the kind of place he had dreamed of for so long. The new Guy Savoy is an airy, summery, vaguely Scandinavian-looking place, done in dark green, dark rosy brown and medium-dark wood tones. There is good art on the walls. Savoy even has his own private Villeroy & Boch china, designed for him by Jean-Pierre Hanki and jazz drummer/artist Daniel Humair (whose work is also on the walls).

The food? Ruinously expensive, but as good and finely detailed as ever--though perhaps, a bit more solid, a bit less ephemeral than it was before. The first little nibble of a recent menu degustation at Savoy’s hands started with two perfectly sweet little cherry tomatoes in a bit of thick tomato juice--sheer summertime in the mouth. The dinner itself proceeded thus: a round, just-made piece of feuillete dough coated with asparagus coulis and criss-crossed with pencil-thin asparagus spears and dotted with thinly sliced, barely-cooked scallops; a piece of very young, very mild wild salmon roasted with sea salt, accompanied by a wonderful little baked potato stuffed with chive butter; half a baby lobster in an elegant light lobster sauce with peas, fava beans, thin green beans, zucchini and carrots; a Savoy classic of lightly browned sweetbreads with black truffles and thinly sliced potatoes; a plump duckling, simply roasted and rare, with an understated broth-like sauce flavored with black and white pepper, mace, and coriander, and the usual profligate array of Savoy desserts--of which a grapefruit terrine with tea sauce was the most surprising and maybe best.

Savoy’s old restaurant on the rue Duret remains open under his management and under the name simply of “Duret.” He plans to sell it, he says, because the new place is taking up all his time and energy.

Bernard Pacaud was chef at the then-three-star Paris restaurant Vivarois until he left in 1983 to open his own L’Ambroisie, on the quai de la Tournelle. It was minuscule and very gray in an Italian-contemporary sort of way, and I never much cared for the way it looked. I did like the food--but it always seemed very simple and straightforward to me, and, frankly, I wasn’t at all sure that Pacaud deserved two stars (especially when he got his second before the masterful Savoy did).

In his new home--a lovely two-room place, vaguely 18th-Century-looking (and very romantic with its old stone walls, marble door frames, tapestries, luxuriant displays of flowers, and well-placed candlelight) on the historic place des Vosges--Pacaud seems to be considerably more inspired. His cooking is still simple and without device, but it is marvelously concentrated, superbly balanced, rich with guileless flavor.

The complimentary appetizer or amuse-gueule here is Pacaud’s famous (and famously simple) sweet red pepper mousse in acidulated tomato sauce--fresh and delicious. His first courses include medallions of lightly smoked salmon, grilled and posed on a scattering of match-stick potatoes, with a dollop of dill cream resting in the background; crab ravioli in a deeply flavorful seafood broth, and a stunning ragout of fresh spring vegetables in a butter sauce with fresh juniper berries and coriander seeds. As main dishes, Pacaud might offer flawless roast turbot with a curry-flavored spice crust alongside a light artichoke puree; a juicy, meaty loin of lamb roasted with thyme, accompanied by parsley-filled potatoes Anna and garlicky sauteed spinach, or spectacular oxtails, wrapped in caul fat and glazed with a rich red wine reduction, served with pureed celery. Desserts are such as a classic mille-feuilles filled with vanilla cream and a thin, crunchy, semi-sweet chocolate tart that suggests brownies for grown-ups. This is surely two-star food, and particularly good and satisfying two-star food at that. The incomparably more complicated and lapidary Guy Savoy, on the other hand, might well--with his move into the old Le Bernadin--be inching toward three.

Guy Savoy, 18 rue Troyon, 17th arrondissement, tel. 43.80.40.61. Dinner for two, food only, $105-$250.

L’Ambroisie, 9 place des Vosges, 4th arrondissement, tel. 42.78.-51.45. Dinner for two, food only, $70-$175.