By Tom Sietsema Washington Post Magazine Sunday, October 16, 2005 A man in a starched white chef's jacket strolls through the dining room carrying an earthy harbinger of fall: "The season's truffles!" trumpets owner Luigi Diotaiuti. All smiles, he holds out a bowl of what look like white rocks; their intoxicating perfume reminds you they're the kitchen equivalent of gold (and best enjoyed, shaved, over risotto). Despite its cramped and sometimes noisy quarters, Al Tiramisu remains the city's most joyful Italian experience. Part of this mood is encouraged by the convivial and attentive staff up front, but the cooks play along, too. They grill a fabulous veal chop, offer fish so fresh it almost flaps (look for treasures like turbot or Dover sole) and do pasta proud, be it ravioli filled with butternut squash and draped with a smooth walnut sauce, or tender gnocchi in an onion-sweetened tomato sauce. Dessert is a no-brainer: Just repeat the restaurant's name.