Where to eat in Beijing, Hong Kong, and Xian?
Eat on the street. Ride the subway to outside of 4th ring and eat from the vendors who line up their tricycle carts outside the stations. You'll need to be there between 7am-9am or 4:30pm-7pm. Line13, LongZe, [where I live] has over 20 vendors serving about a dozen different things. Breakfast/am choices are mostly bread-type-thing plus egg or meat with differing paste-consistency sauces.