Shanghai's famous specialty dim sum was founded in the early 20th century. It is called "crab shell yellow" because it is shaped like a crab shell and its color is as deep red as the back of a crab shell after cooking. Crab shell yellow is made of pastry noodles and fermented noodles, and then made into a flat circle, and then a layer of sesame is glued on the surface, and it is pasted on the furnace wall and baked. The fillings are salty or sweet, and the finished product is shaped like a crab shell, golden in color, crispy on the outside and sweet on the inside.