Make the sauce: Combine oyster sauce, light soy sauce, dark soy sauce, salt, and sugar.
Steam the noodles: In a wok, boil water and steam the noodles for 10 mins with the lid on. Uncover the wok and transfer the noodles into the same water that was steaming it. Cook for 5 mins, then drain.
Prepare the wok: Heat a clean wok on high and when it’s hot enough, add oil.
Cook the noodles: Throw in the noodles, spread them out, cook for 30 secs, then flip and cook other side for 30 secs.
Add char siu: Push the noodles to one side of the wok, and add char siu and a dash of oil to the freed up area. Stir-fry without mixing into the noodles for 20 secs.
Add vegetables: Add the onion, carrots, celery, and king oyster mushrooms, stir-fry for 40 secs.
Cover vegetables with noodles: When the vegetables are fragrant, move the noodles on top to cover them. Cook like this for another 40 secs.
Pour the sauce and mix: Now pour the sauce over the noodles, then mix and stir-fry everything together for 60 secs.
Final touch: Finally, add beansprouts and sesame oil. Cook for another 2 mins on medium heat and it’s ready to eat.