Ingredients:

8 oz beef tenderloin (thinly sliced)
2 tablespoons cooking oil
2 stalks leeks/scallion (sliced diagonally)
1 inch ginger (finely chopped)
3 cloves garlic (thinly sliced)

Marinade:

1 teaspoon corn starch
1 teaspoon soy sauce
1 tablespoon water
1 teaspoon Chinese cooking wine (rice wine or Shaoxing wine)

Sauce:

2 teaspoons oyster sauce
2 tablespoons soy sauce
1/2 teaspoon dark soy sauce
3 dashes white pepper powder
1/4 teaspoon sesame oil
1/4 teaspoon Maggi seasoning
1 tablespoon sugar or to taste
Salt to taste