Tangniu mutton is a unique and famous snack in Xi 'an Anfangbang. Xi 'an Laosunjia Restaurant has been in business since 1898, with a history of one hundred years.

According to legend, beef mutton soup evolved from the ancient "beef mutton soup" in 1 1 century BC. In the Western Zhou Dynasty, "beef and sheep soup" was listed as a "gift" for emperors and princes. According to the Book of Song Dynasty, in the Northern and Southern Dynasties, Mao Xiu presented delicious beef and sheep soup to Song Wudi, and Emperor Wu was awarded the title of Taishigong. Later, he was promoted to Doctor Guanglu of Shangshu. There is also an interesting legend that Zhao Kuangyin, the Emperor of the Song Dynasty, was trapped in Chang 'an before he proclaimed himself emperor, and lived a life of starvation all day. One day, he came to a store where beef and mutton were being cooked. The shopkeeper felt sorry for him, so he told him to break his dry buns, then poured him a spoonful of hot broth and cooked it thoroughly on the fire. Zhao Kuangyin wolfed down his food and thought it was the best food in the world. Later, Zhao Kuangyin put on a yellow robe and became an emperor. One day, when he passed by Chang 'an, he still didn't forget the beef and mutton buns he had eaten here in those years. Wu purposely found this store to eat beef and mutton buns in soup, which was delicious, better than delicacies, and rewarded the owner of this store. As soon as the story of the emperor eating steamed buns spread, beef and mutton became a famous snack on Chang 'an Avenue. Su Dongpo, a great writer in the Northern Song Dynasty, once wrote a hymn: "There is bear wax in the dragon's stomach, and Qin only cooks mutton soup."