In a wok, heat the vegetable oil over medium until hot. Add the ground beef and stir-fry, breaking it up with a spatula, until the meat is browned and cooked through. Add the Shaoxing wine and ginger and fry until fragrant.
Reduce the heat to low, then add the sweet wheat paste, doubanjiang and five-spice powder. Stir-fry until the beef is evenly coated in the sauce, about 2–3 minutes.
Deglaze the wok with half the stock (or water), bringing it to a light simmer over medium heat. Simmer for about 7–8 minutes until the sauce is reduced. Add the remaining stock and simmer for another 8–10 minutes. At this point, the beef should still be saucy, not dry, as it provides most of the sauce for the noodles. Set it aside while you prepare the sauce and cook the noodles.