Duo has the trappings of a simple neighborhood bistro — but one with a particularly inventive cook behind the grills. Chef John Broening can do French, as evidenced by his duck confit over potato pancakes with apricot mustard. He can do Italian (gnocchi with oyster mushrooms and pecorino), fusion (a dish of pastry-wrapped mahi with herb pistou and sautéed vegetables). And he clearly knows his way around the fine points of old and new Continental, greenmarket and straight-up American cuisine (parmesan-crusted chicken with bacon-shot potato salad and watercress). Add to those talents a pastry department run by Yasmin Lozada-Hissom (one of the best pastry chefs anywhere), and the result is the most intelligent, consistently well-executed and grounded New American menu in the city.