I made an account just to comment on this post, because it came up when I searched for “inner mongolian food” 
My family is from Inner Mongolia and I don’t get many chances to visit so I was really excited to hear that an Inner Mongolian youmian (oat noodle) chain was coming to Arcadia. Unfortunately, I thought the food was pretty average overall, and would much rather go to MJOY to get my lamb fix.
The two dishes I tried that seemed pretty good and authentic were the youmian yuyu (needle/fish shaped noodles) and the sticky rice dessert. The lamb shaomai were average, but I sort of expected that because the star of the dish is the fresh, meaty flavor of Inner Mongolian lamb (zero gaminess), and I don’t think it’s easy to recreate or imitate that in America.
The low point of the meal was the dish I was most looking forward to, the youmian wowo (honeycomb shaped noodles). It came covered in this weird tomato-based sauce that was super sweet and made the wowo super soggy, more like a bad pasta sauce than something that belonged with youmian. From some googling, it seems like the Xibei stores in China also have the same dish, which is surprising to me because it tasted like something they had done to try and appeal to the American palate.
Anyway I got the chance to visit Hohhot/Inner Mongolia afterwards and had some amazing youmian and Mongolian food, where I dunked steamed wowo noodles in a variety of flavorful lamb and beef-based soups/sauces, just like how I remembered from my childhood. Ironically my relative told me that everyone he knows hates Xibei because the flavor just doesn’t taste “right” to them and apparently it’s the more expensive, more “elevated” youmian place to go to if you want to show off.
Editing to show a pic of a youmian meal in china, but not at Xibei. You’re supposed to create a mix of potato/eggplant + lamb/beef broth + random pickles, and then dip the various styles of youmian into that to eat it. Granted, this is pretty fancy and what I remember from cheap places 20 years ago was more like just the noodles and a big bowl of soup.
