Pour the vegetable oil in a large non-stick pan or wok and place it over medium heat until the oil is hot. Then add the halved Brussels sprouts together with the mashed garlic and sliced onion.
Stir well. Gently fry the vegetables for 4 minutes. Chop the green beans into bite-size bits. Slice the carrot. Add both green beans and carrots to the sprouts in the pan also.
Stir well. Let the colorful vegetables gently fry for 3 more minutes. Don’t burn them. Then sprinkle the vegetables with the oyster sauce, soy sauce, sesame oil and fish sauce. Add 3 tablespoons of water. Season the vegetables with a pinch of pepper.
Stir the vegetables well again and cook them for another minute. Add the precooked noodles.
Stir fry the vegetables and noodles for 3 minutes. Then check the seasoning and add extra pepper, oyster sauce, fish sauce, soy sauce or sesame oil to taste if necessary.
Take the wok off the heat and scoop the stir fried Chinese egg noodles and vegetables into large bowls. Drizzle with the remaining oyster sauce marinade if there’s any left in the wok. Sprinkle the noodles with sesame seeds and serve immediately.