Nguyen Restaurant 381 15th St./Franklin St.; downtown. The large, open, curry-yellow dining room here is furnished with jack wood tables and chairs made by the owner’s family in Viet Nam (customers can place special orders). Portions are generous and service is fast. Among the outstanding Vietnamese items are deep-fried imperial rolls, lotus root salad topped with peanuts and a side of shrimp crackers, hot-and-sour soup, Vietnamese coconut milk-shrimp curry, and a vegetarian special of tofu sautéed with eggplant and onions in spicy plum sauce. Pho noodle dishes, rice plates, and exotic French iced black coffee and lotus leaf hot tea are also on the exceptional menu.