Since opening at the end of last year, this small 17-seat establishment has won a crowd of followers and sells an average of 600 roujiamo a day including online orders, according to Kong Long, head chef of Xibei's roujiamo project.

"Chinese roujiamo are closely associated to Western hamburgers. Two pieces of bread, with meat in between. If burgers can prevail as fast food in the West, why not Chinese burgers?" he says. Current dishes on offer include the signature stir-fried spicy veal in a baked bun (32 yuan), grilled lamb shashlik (33 yuan), stir-fried tomato and egg (16 yuan), and stir-fried rattan pepper chicken (26 yuan).

Kong says the fillings they have developed cater to different preferences and palates, whether they be spicy, light or vegetarian. And some more refreshing fillings will be added as the weather becomes warmer, such as Chinese shredded potato salad sandwiched in a bun.

The spicy veal filling stands out with its chunks of juicy meat and a sprinkling of mild peppers, but the other flavors are equally impressive, thanks to the sublimely chewy and soft crispy buns.

The bun (mantou), or "mo" in some northwestern dialects, is made with traditional leavening techniques without the addition of yeast or baking soda, says chef Kong.