The culinary trademark of Ruggles Grill [903 Westheimer, (713)524-3839] and most of its siblings [Bistro Latino, 711 Main, (713)227-9141; Enron Field, 333 Crawford, (713)259-8080; and Grille 5115 in Saks Fifth Avenue at the Galleria, (713)963-8067] is the massive medley of Southwestern-style vegetables that accompanies every entrée. But only one thing matters on that mountainous plate of food, and it's decidedly French. Ruggles's potatoes au gratin, the magnifique mainstay of all its meat dishes, starts with a casserole, greased with roasted garlic butter, to which thin-sliced Red Bliss potatoes are fanned in an artful creation that is layered with more roasted garlic, heavy cream and a mixture of mozzarella and Parmesan that you would swear is goat cheese. "We wish," says Ruggles's chef de cuisine Doug Atkinson with a laugh. "But that would be too expensive."