It's found in most places in the southwestern part of Shanxi and Shaanxi, and in some places in the western part of Henan, but it was first a secret recipe for a staple food that was accidentally acquired in the Shangdang area of the southwestern part of Shanxi. It's just that people in the southwestern part of Shanxi pay more attention to the noodle category, so there's less of it for buns (cakes), while Shaanxi, especially near Xi'an, is vigorously developing its snack industry under the impetus of tourism, creating a sense that mutton buns are a specialty of Xi'an, Shaanxi.