Cook the noodles: Boil according to package directions until just tender. Do not overcook. Drain, rinse quickly under cool water, and toss with a tiny drizzle of oil to prevent sticking.
Make the sauce: In a small bowl, whisk soy sauces, oyster sauce, sesame oil, sugar, rice vinegar, pepper, and water. Adjust sweetness and salt to taste.
Prep the vegetables: Keep slices thin and uniform so they cook quickly.
Separate the green onion whites from the greens.
Heat the pan: Place a large skillet or wok over medium-high heat. Add 1 tablespoon oil until shimmering.
Stir-fry aromatics: Add garlic, ginger, and green onion whites. Stir 20–30 seconds until fragrant. Don’t let them brown.
Add hearty veggies: Toss in mushrooms and carrots.
Stir-fry 2 minutes until they start to soften.
Add quick-cooking veggies: Add bell pepper, snap peas, and cabbage. Stir-fry 2–3 minutes, keeping everything crisp-tender.
Combine with noodles: Push veggies to the sides, add the remaining 1 tablespoon oil if needed, then add noodles. Toss well.
Pour in sauce: Add the sauce and chili garlic sauce (if using).
Stir continuously 1–2 minutes until noodles are coated and glossy. If dry, splash in a tablespoon of water.
Finish and serve: Turn off heat. Stir in green onion tops.
Taste and adjust seasoning. Top with sesame seeds and serve hot.