2Add the flank steak to a bowl with the marinade ingredients: 1/2 tablespoon of dark soy sauce, 1 tablespoon of white cooking wine, 1/2 tablespoon of soy sauce, 1/4 teaspoon of baking soda, 1/4 teaspoon of white pepper, and 3 tablespoons of cornstarch.
3Mix until fully coated and let it marinate for at least 15 minutes.
4In a separate bowl, mix together all the sauce ingredients: 1 tablespoon of oyster sauce, 1/2 tablespoon of dark soy sauce, 1/2 tablespoon of soy sauce, 1 teaspoon of chicken bouillon, 2 teaspoons of sugar, 1/2 teaspoon of white pepper, and 1 teaspoon of sesame oil. Set aside.
5Heat 1/3 cup of oil in a pan or wok over medium-high heat.
6Fry the marinated beef, spreading it evenly, and cook for about 3 minutes per side.
7Remove the cooked beef from the pan and set aside.
8In the same oil, add 5 minced garlic cloves and 1 teaspoon of grated ginger. Sauté for about a minute until fragrant.
9Then add in 1 sliced white onion and sauté for about 2 minutes or until slightly translucent.
10Pour in the prepared sauce and let it simmer for 1-2 minutes until glossy and thickened.
11Add the cooked beef back into the pan and toss to coat evenly in the sauce.