Nui is the Vietnamese word for macaroni, xao means to stir-fry and Bo means beef. So it’s basically stir-fried macaroni with beef. Nui was introduced to Vietnam by the French as the word Nui is derived from a French word nouille.
If you buy a Nui package in Vietnam, it tastes slightly different than the Italian pasta you can buy in the West as they do add some sort of rice flour in making the pasta dough. Anyway, this recipe works for whatever kind of macaroni you can get.
Locals like to use a soy sauce (Nước Tương) to make it taste even more distinctly Vietnamese style.