Prepare the ingredients: Thinly slice the beef knuckle steak, about ⅓ inch thickness. Slice the onion and finely mince the garlic cloves.
Marinate the beef steak: Add the following ingredients in a small bowl: Oyster sauce, soy sauce, brown sugar, black pepper, salt, baking soda, rice vinegar, sesame seed oil, and water. Whisk the marinade ingredients with a fork or a spoon. Then, prepare a large bowl to marinate the beef steak. Add the steak and the marinade mixture to the bowl, mix everything using your hand, and marinate for thirty minutes.
Stir-fry the ingredients: Preheat a wok to medium-high heat, add olive oil, add the onion and garlic, and sauté the aromatics for three minutes while stirring occasionally. Thereafter, add the beef steak with the marinade sauce. Stir thoroughly to mix all the ingredients. Continue to cook the steak for ten minutes on high heat while stirring every minute. Garnish with sesame seeds to serve.