Stir in the oyster sauce and cook for 2–3 minutes. Add about half of the reserved broccoli cooking water and crumble in half of the chicken stock cube. Bring to a simmer and then add the sesame oil.
Add the chicken, ginger, mange tout and bean sprouts and flip-fry for 2 minutes. Add the noodles, soy sauce, oyster sauce, salt, sugar and a spoonful of the mushroom water and flip-fry for 2 ...