Xi'an City, Shaanxi Province. Mutton Bun, also known as Boiled Bun, Mutton Bubble and Mutton Bun, is made with the main ingredients of mutton, minced green onion, vermicelli (or vermicelli), sugar and garlic, and is a famous snack in Xi'an City, Shaanxi Province. Its history can be traced back to the Tang Dynasty period, when teahouses and restaurants in the city of Chang'an were already making the delicacy. By the Song Dynasty, mutton buns gradually became a specialty of Xi'an and have been handed down ever since. In Xi'an, people often savor this dish on important occasions or when meeting with friends to express their respect and friendship for each other.