Cook the Noodles: Bring a pot of water to a boil and cook the chow mein noodles according to the package instructions. Drain and rinse them under cold water to stop the cooking process.
Prepare the Sauce: In a bowl, mix the cornflour, dark soy sauce, Chinese rice wine, kecap manis, hoisin sauce, beef stock, sesame oil, and white pepper together until combined. Set aside.
Heat the Wok: Heat 2 tablespoons of sunflower oil in a wok over high heat until shimmering. This quick process helps achieve that desired stir-fry quality.
Stir-Fry the Steak: Season the thinly sliced steak with garlic salt and black pepper, then add it to the hot wok. Stir-fry for 2-3 minutes until just cooked through, then remove and set aside.
Cook the Vegetables: Pour the remaining tablespoon of oil into the wok, then add the sliced onion, minced garlic, and matchstick carrots. Stir-fry for about 3 minutes until the vegetables begin to soften.
Add More Veggies: Toss in the green bell pepper, savoy cabbage, and beansprouts. Continue stir-frying for an additional 2 minutes until they’re vibrant and tender-crisp.
Combine Everything: Return the cooked steak and drained noodles to the wok. Pour the prepared sauce over the mixture and gently toss everything together until well combined and heated through for about 2-3 minutes.
Serve and Garnish: Spoon your delicious beef chow mein onto plates, and garnish with fresh chopped spring onions, a sprinkle of sesame seeds, and chili flakes for an extra kick if desired.