Every time a new French or Italian restaurant opens on the K to M Street corridor, one wonders what they could offer that is not already available. Thus, I1 Giardino could be considered this year's Tiberio. But that is hardly something to complain about; when it comes to good restaurants, we can use all we can get. So far so good with I1 Giardino. The room is handsome, with decorative tiles on the floor and the walls lined with antique sideboards and fair-to-good modern paintings. Spacious tables are set with gorgeous flowers and tableware of admirable quality. In preparation at press time were a garden and a room overlooking it. The menu is so comprehensive, from hot and cold hors d'oeuvres to pastas to meats, fish, vegetables, salads and desserts, each with close to a dozen possibilities, that you will want to spend considerable time poring over it. Over pasta, of course, perhaps a half-portion of spinach-stuffed agnolotti to start.But then the mozzarella melting in a deep-fried bread boat and drizzled with anchovy butter is irresistible. Lamb chops are superb, veal flawless, fish exceptional - particularly with a powerful fennel sauce piquant with vinegar. Vegetables receive special attention. And the desserts, from the chocolate-drenched profiteroles to the rum-drenched zuppa inglese, deserve serious attention even if you have already eaten your fill. The fly in this ointment is the price - very high, from the antipasto through the wine list. And the kitchen at lunchtime has no care for your working schedule. But the dining room operates like a well-oiled machine, and the food is worth the wait.