Xibei serves Shanxi specials and has many outlets all over Beijing. I call it Chinese fastfood because of the large crowds, the queing and the rather cheap prices. My visit was on 7 January 2016.
I had to wait for well over 20 min. at the Ginza Mall outlet (Dongzhimen), made interesting as I could watch some of the cooks preparing the food. All pretty well organized and clean.
I was told the “long-hour stewed fish” was recommended but by the time we ordered they had run out. Oh well next time.

The dishes were pretty good and I liked their popular cold noodle dish, among others. Price very reasonable: no drinks (free water) and food (plenty) for two: some RMB 110.
Always puzzling why some restaurants are so popular while others remain rather empty. One of the mysteries of Beijing, at least for me.