When Erwin and Doris Mei operated King Fung Garden in Chinatown, they won a following for scallion pancakes, Shanghai chow mein, and more — but especially for Peking duck. In 2008, they left Chinatown for Brookline, opening King Fung Garden II. Now they return to their original neighborhood with China King. The new menu looks familiar. It has the scallion pancakes, Shanghai chow mein, and rice cakes with pork and cabbage — and, of course, the Peking duck.