NOODLES: Bring a large stockpot of water to boil. When boiling, add noodles and boil according to package directions. Drain and rinse under cold running water. Prepare the veggies while noodles boil.
VEGGIES: Separate the greens from the whites of the scallion. Cut into one-inch pieces then quarter the 1-inch piece vertically so you end up with thinly julienned scallions; set aside.
SAUCE: In a bowl, combine the oyster sauce, soy sauce, sugar, minced garlic, red pepper flakes (or chili crunch), salt, and 1 tsp of sesame oil. Stir to combine; set aside.
STIR FRY: Heat a large wok or a 16-18 inch skillet over high heat. Let the skillet heat for several minutes until SCREAMING HOT. Drizzle with 1 tbsp sesame oil + 1 tbsp high heat oil. When the oil shimmers, add noodles in a thin even layer. Grab the handle, swirl the pan so the oil evenly coats all the noodles. Cook noodles for 4-6 minute untouched, or until golden and crispy.
FLIP: The noodles over using a large spatula. Do this carefully in portions if necessary. Drizzle the remaining 1 tbsp of sesame oil + 1 tbsp of high heat oil around the perimeters of the pan and again, lift the skillet with handle and swirl the pan to allow the oil to distribute. Cook noodles for 3-5 minutes. Remove noodles to a plate.
SAUTE: Heat the remaining 1 tsp of sesame oil, along with the white portion of the scallion for 10 seconds. Add the shredded carrots (if using) and let cook for an additional 10 seconds. Add the noodles back into the skillet and toss. Separate the noodles so there aren't any large clumps. Toss in the cabbage mix.
ADD SAUCE: Drizzle with the soy sauce mixture and toss continuously for 1-2 minutes or until the sauce distributes evenly over the noodles.
FINISH: Add the bean sprouts if using and the greens of scallions. Toss to combine and serve immediately.