Prepare the Marinade: In a medium bowl, combine beef strips with soy sauce and cornstarch, ensuring they are well-coated for flavor and moisture retention. Let the beef marinate for at least 10 minutes while you prepare the vegetables.

Sauté the Onions: Heat 1 tablespoon of oil in a hot wok over medium-high heat. Add the sliced onions and stir-fry for about 3-4 minutes until they turn translucent and slightly caramelized. Remove the onions from the wok and set them aside.

Sear the Beef: Increase the heat to high and add another tablespoon of oil to the wok. Add the marinated beef strips, spread out in a single layer. Sear for 3-4 minutes until browned on one side, then toss to cook for another 2-3 minutes.

Create the Flavorful Sauce: Mix together minced garlic, grated ginger, soy sauce, and oyster sauce in a bowl. Pour the sauce mixture into the wok, stirring quickly to coat the beef. Cook for about 2 minutes until the sauce thickens slightly.

Combine Ingredients: Return the caramelized onions back to the wok, stirring gently to integrate. Cook for an additional 1-2 minutes to ensure everything is heated through.

Serve and Enjoy: Remove from heat and serve hot over steamed rice or noodles.