Heavy drapes shield the gastrophile's Shangri-La, Café Chambord, from New York's busy, El-less Third Avenue (near 50th). Within, the decor is underplayed to the point of refined Spartan, lest there be any distraction from the shrine's devout purpose. The high lama here is Phil Rosen, a dedicated perfectionist who lives to see that some of the world's finest food is served and enjoyed. It is. After champagne cocktails, our hors d'oeuvres were Coquille Gratinée, a merely sublime melange of scallops, lobster chunks, mushrooms and cheese sauce; Mademoiselle chose a CrèpFarcie, a wine-ennobled crab meat and lobster pancake. Our entrée was a Filet de Boeuf en Tranches, Bordelaise, so tender that we felt it understood; Mademoiselle chose Poulet sauté à la Fine Champagne, which is chicken adorned as bird of paradise and anointed with the best cognac. She raved. Dessert was a soufflé for two, drenched in a sauce of vanilla and Grand Marnier. Victor, the sommelier, suggested with gentle gravity the proper red and white wines, which included a young rosé from Provence and a crisp chablis. The tab was not small, but then we were not dealing with the short-order school of cuisine. Open every day (except Sunday) for luncheon and dinner. Most stimulating news of all is that non-Gothamites can sample the fantastic fare via the mails. Chambord frozen foods, no relation to TV dinners, include sauces (bigarde, périgourdine, veronique, et al.), soups (potage St.Germain, bisque homard, et al.) and entrées (caneton a l'orange, homard grille beurre viquerons, et al.) that come to you packed royally in dry ice, ready to pop in the oven. The management will whisk off an order blank at your request.