short for mutton bubble and steamed bun. Known as "sheep soup" in ancient times, it is delicious in the northwest, especially in Xi 'an, Shaanxi Province, where beef and mutton are the most famous in paomo. Su Shi, a famous poet in the Northern Song Dynasty, left a poem that "there is bear wax in the soup, and the Qin Dynasty cooks only sheep soup". It is well-cooked, the ingredients are heavy and mellow, the rotten meat soup is thick, fat but not greasy, rich in nutrition, full of fragrance, attractive appetite and endless aftertaste after eating. Because it warms the stomach and resists hunger, it is always loved by people of all ethnic groups in Xi 'an and northwest China, and foreign guests come to Shaanxi to try it first to satisfy their appetite.