Open: The Mayfair: Monday through Saturday for dinner only 7 to 10 p.m. Three-, four-, five- tableside meals for $50, $65, $80 and $79. The Grill: Monday through Friday for lunch noon to 3 p.m., for dinner seven days a week 6 to 11 p.m. Appetizers $6.50-$8.75, entrees $11.50-$17.50, desserts $3.50-$4. The Promenade: Monday through Saturday for breakfast 7 to 10 a.m., $4.25-$12.75; for lunch 11:30 a.m. to 2:30 p.m., $7.25-$18.75; Sunday breakfast 7 to 10:30 a.m. and brunch 10:30 a.m. to 2:30 p.m., $12.75- $18.75. MC, AE, V, CB, D. Reservations suggested. Average dinner at The Mayfair with wine, tax and tip about $120 a person; at The Mayfair Grill about $50; brunch at The Promenade about $20.

Washington's avant-garde French restaurants have a new contender. And when the young German chef at The Mayfair adds more Washington experience to his prodigious imagination and skill, his restaurant could run neck-and-neck with Le Pavillon and Jean- Louis, his most obvious competitors. The problem is that he is already neck-and-neck in price, with fixed-price dinners from $50 to $80 and dinner checks likely to run well over $100 a person. There's not much room for inexperience at that rate.

The Mayfair is one of The Regent Hotel's three dining rooms, each handsome in a different way. Only The Promenade is open for Sunday brunch, and its environment -- comfortable chairs, acres of space, modern chandeliers and a view of the flower-decked atrium -- makes it luxurious at midday. Brunch begins with live chamber music and a highly respectable champagne. But brunch dishes sound far more interesting than they taste, from the salty, compact quail terrine to the none-too-fresh smoked fish to the prime rib, soft and dry and with all taste leached out of it. Brioche of Salmon, Scrambled Egg with Lobster Sauce suffered from too-strong salmon and eggs, and the lobster sauce was lost. Eggs benedict were perfectly textured but their hollandaise badly needed lemon. And so it went, from bready danish to crumbly pastries. Here and there a vegetable was delectable, a raspberry torte richly good, a fruit platter ripely beautiful. But the overall impression of beauty and comfort had little to do with the food.

In the dark mahogany room of The Mayfair Grill the imbalance was intensified. Asparagus soup was bland, and appetizer salads of smoked fish, smoked duck and tasteless tiny shrimp were lost in their beds of excessive and underdressed greens. Among main dishes, lamb was grainy and dry, both as chops and filets; steak was of good quality but cut thin and not seared. The meat stuffing for a chicken breast tasted bland and wet. And although various sauces were agreeable, they could not compensate for the deficiencies of what they were saucing. With such a small menu -- seven main dishes plus a couple of specials -- each dish should be a showcase of the chef's talent, but The Grill serves merely good food at prices that warrant much better food.

The restaurant to watch is The Mayfair. The modern dining room looks luscious, with beveled mirrors and a ceiling swathed with tucked fabric the color of salmon mousse. The room is comfortable, generously proportioned and polished in every detail -- from the perfectly ripe cheeses, each under its crystal bell on a side cart, to the staff who move with sureness. The food, as original as the setting, is presented in a parade of from three to seven tiny courses. Each is a show: perhaps a small round of minced swordfish tartare with caviar in three colors; or tiny, fluted beet-stuffed ravioli in a pool of pink beet sauce -- a supernal borscht. Belon oysters were each topped with a different vinaigrette, the tomato- and the truffle-flavored ones outstanding (though the oysters needed to have been loosened from their shells).

This chef is a master at color and has a playful imagination. Instead of serving a mere sorbet to refresh the palate between courses, he presents a "dialogue of fruits," a plate of boldly hued and delightfully refreshing chilled fruit purees that swirl and blend like fingerpaints as you spoon them. His soups might be a light and pretty cupful of intensely flavored tomato consomm,e or ivory coconut with pink morsels of lobster and brilliant green parsley quenelles.

Fish courses are small rectangles of pearly perfect, supple fish with crisped skin; shrimp and langoustine burst with taste. Vegetables are diced into impeccable little cubes and infused with flavor; here ratatouille is a delicate eggplant garnish rather than a strongly seasoned Mediterranean stew.

Meat dishes look routine but yield subtle surprises. A pink and juicy thick venison filet on a bed of enoki mushrooms was moistened with a sauce of apple, calvados and venison stock, just faintly sweet. Pigeon breast was tender, pink and gamey, sparked by a bed of strong raw greens just wilted by the heat. While the choices of meats are only about four each night, they offer interesting variety -- veal loin in duck liver sauce or duck breast with apple compote, for example. And only one, tenderloin of beef with shallot sauce, has been pedestrian.

As for desserts, there are some intriguing possibilities: fresh dates peeled and halved, piped with white chocolate mousse on a mocha cream; thick English custard studded with oranges and star fruit, glazed to a golden brown; a warm, freshly constructed plum tart on armagnac sabayon. And there are tiny, fragile custard barquettes with perhaps two blueberries and one golden raspberry. Imperfections, sure: white and dark chocolate mousse looked as if a two-color egg had been halved and berries spilled out of it, but it had little flavor.

Some elements depend on clever purchasing rather than cooking. The cheeses deserve applause; they are perfectly ripe and uncommon selections. The wine list has some astonishing vintages -- at prices to match -- and also some carefully chosen options at modest price. But the rolls are soft and textureless; surely better can be found.

Keeping in mind that these beautiful little dishes are expensive, standards must be exceptionally high. Although the kitchen seems surer as time goes on, some flaws continue, particularly in an underseasoning of first courses. A tiny dish of carpaccio was sliced so thin it could hardly be tasted and seemed seasoned with nothing but olive oil. The same blandness felled the salmon marinated with truffles. And twice the ginger sauce for fish tasted more of something else -- cream or yellow peppers -- than of ginger. A duck liver and sweetbread terrine, too, showed more richness than flavor. When the chef sharpens his seasonings (as with pompano in balsamic vinegar butter) he can create a memorable balance between strong flavors and delicacy.

The Mayfair has some exceptional and extraordinarily beautiful food. The chef is clearly both expert and imaginative, but he is still unseasoned; he himself said it takes years for a restaurant to become really fine. Does one recommend risking $125 a person for dinner? Only if doing so is accepted as an adventure. The Mayfair is a restaurant that needs to prove itself, but certainly could prove exciting.