Slice the beef thinly and marinate it with soy sauce and cornstarch for 15–20 minutes.
Heat oil in a wok or skillet and stir-fry the beef until browned. Remove and set aside.
In the same pan, sauté minced garlic and grated ginger until fragrant.
Add sliced mushrooms and cook until they become tender and release their moisture.
Stir in soy sauce, oyster sauce, and a splash of water to create a flavorful sauce.
Return the beef to the pan and toss until evenly coated and heated through.
Garnish with sliced green onions and serve hot with steamed rice or noodles.