Cook the Lo Mein noodles according to package directions until just tender. Drain them immediately and rinse with cold water to stop cooking. Toss lightly with 1 teaspoon of vegetable oil to prevent sticking.
Prepare the sauce: In a small bowl, whisk together the soy sauce, oyster sauce, sesame oil, sugar, and white pepper. Set aside.
Heat the remaining vegetable oil in a large wok or skillet over high heat until shimmering.
Add your chosen protein (if using) and stir fry until cooked through, about 3-4 minutes. Remove the protein from the wok and set aside.
Add the garlic, ginger, and the white parts of the green onions to the wok. Stir fry for 30 seconds until fragrant.
Add the carrots and broccoli. Stir fry for 2 minutes.
Add the cabbage and stir fry for 1 minute until vegetables are crisp-tender.
Return the cooked protein to the wok. Add the cooked noodles.
Pour the prepared sauce mixture over the noodles and vegetables. Toss everything together quickly and constantly for 1-2 minutes until the sauce evenly coats the noodles and everything is heated through.
Stir in the green parts of the green onions just before serving.
Notes
For a vegetarian version, substitute tofu for meat and use vegetarian mushroom sauce instead of oyster sauce.
Do not overcook the noodles; they should have a slight chewiness (al dente).
Use high heat for stir frying to achieve the best texture and flavor.