Slice the beef against the grain.
Transfer the beef slices to a bowl and add all the marinating sauces except the oil. Grasp with hand to make sure beef slices absorb the marinating sauces. Then coat with 1 tablespoon of vegetable cooking oil. Set aside to marinate at least 15 minutes. You can also prepare the marinating beef in ahead and place it in fridge overnight.
During this time, remove any tough skin of the Chinese broccoli. And then cut into sections with angle. Separate the leaves too. Bring water to boil in a large pot, add 1 teaspoon of sesame oil and a small pinch of salt (this step can help to keep the green color of the leaves and the crunchy texture, applying to all dark leafy vegetables ). Add Chinese broccoli in, stem firstly and leaves secondly. Blanch Chinese broccoli until the water boils again. Transfer out and drain.
In a small bowl, mix oyster sauce, dark soy sauce, sugar and sesame oil together.
Add 2 tablespoons of vegetable oil in a hot wok with ginger slices (the wok should be heated firstly). Place the beef in when the oil is warm but not hot. Let it stay for a while until the starch finish gelatinization and then fry for a while until the beef changes color (Don't overcook the beef ).
Add stir fry sauce and blanched Chinese broccoli. Mix well and transfer out completely.
Recipe is firstly published in 2015 and updated in 2020.