Bring a large pot of salted water to a boil and cook noodles until just al dente; drain and toss with a little oil to prevent sticking.
Whisk together soy sauce, dark soy, oyster or hoisin, sesame oil, rice vinegar, sugar and stock in a bowl; set the sauce aside.
Heat 1 tablespoon oil in a large wok or skillet over high heat until shimmering.
Add protein (if using) and sear quickly until nearly cooked; remove and set aside.
Add remaining oil, then sauté garlic and ginger briefly until fragrant, about 20–30 seconds.
Add carrots and mushrooms; stir-fry 1–2 minutes until they begin to soften.
Add bok choy or cabbage and the white parts of scallions; stir-fry until greens are wilted but still bright.
Return protein to the pan and push ingredients to the side to heat through.
Add cooked noodles and pour the sauce evenly over everything; toss vigorously to coat and heat through.
Stir-fry 1–2 more minutes, adjust seasoning with salt, pepper or extra soy, finish with green scallion slices and a drizzle of sesame oil, then serve garnished with sesame seeds.