Prepare Noodles:
Soak dried noodles in hot water according to package instructions until pliable (or use fresh rice noodles). Drain and set aside.
Mix the Sauce:
In a bowl, whisk together oyster sauce, soy sauces, fish sauce, sugar, vinegar/lime juice, and chili garlic sauce.
Cook the Beef:
Heat 1 tablespoon oil in a large wok or skillet over high heat. Add sliced beef and sear for 1–2 minutes until browned. Remove and set aside.
Sauté Aromatics & Veggies:
Add remaining oil, then sauté garlic and shallots for 30 seconds. Add bell peppers and optional veggies; stir-fry for 2–3 minutes until just tender.
Combine Everything:
Return beef to the pan. Add drained noodles and pour in the sauce. Toss well over high heat until everything is coated and heated through, about 1–2 minutes.
Finish with Basil:
Turn off the heat and fold in fresh basil leaves and green onions. Let the basil wilt slightly.
Serve:
Plate hot and enjoy immediately. Serve with lime wedges or extra chili if desired.