Authentic Xi snacks are not as easy to learn as you say. Authentic snacks are generally distributed in two types of places. One is the authentic time-honored brands such as "Lao Sunjia" and "Jia San Steamed Bun". Second, small workshops are private or self-employed. If you want to learn, you'd better work in the backyard of these places, but it will be very hard, because people like you can only do odd jobs, and their wages are low and tired. However, Xi 'an seems to have a chain of cold noodle shops. I'm not sure about the details. Xi 'an also has a school that teaches cooking. It's called "Li Tao Culinary Institute", but they mainly teach cooking instead of snacks.