Bring a large pot of water to a boil and cook the pasta just until tender. Drain and chill under cold running water. Shake off excess water and toss with 1 or 2 tablespoons of oil to prevent sticking. Transfer them to ½ of a sheet pan lined with parchment paper.
Season the pork liberally with salt. Let the salt dissolve, then toss the pork with the cornstarch till all pieces are evenly coated. (Do this before you prep the vegetables.)
Combine the soy sauce, dark soy sauce, vinegar, vermouth (or Shaoxing wine), and set aside.
In a wok or large, heavy sauté pan, over high heat add two tablespoons of vegetable oil. When it is smoking hot, add the shiitakes in a single layer. Press down hard on them to sear them, 30 to 40 seconds. Jump them in the pan to cook them on all sides. Remove them to the empty half of the sheet pan.
Add another tablespoon or two of oil to the pan. When it is smoking hot, add the cabbage, carrot, and onion. Try to get a good sear on them. Cook until the carrot is tender, adding the mushrooms toward the end and tossing so that all the ingredients are evenly distributed. Remove the vegetables to the sheet pan.
Using a torch, char the vegetables and noodles. They should smoke pleasantly and blister. Toss and torch again.
Add another couple tablespoons of oil to the sauté pan. When it's smoking hot, add the garlic and ⅔rds of the scallions. Cook, stirring for ten seconds or so, then add the pork and stir fry until nicely colored.
Add the vegetables and noodles to the pork, and toss to combine and reheat the noodles. Add the soy sauce mixture and toss. Remove to a platter, drizzle with sesame oil, top with bean sprouts (if using) and the remaining scallions.