Prepare the Sauce: In a small bowl, whisk together the soy sauce, oyster sauce, rice vinegar, sesame oil, and cornstarch until smooth. Set aside.

Heat the Skillet: Heat 1 tablespoon of vegetable oil in a large skillet over medium-high heat until shimmering.

Cook the Beef: Add the thinly sliced beef and stir-fry for about 2–3 minutes until browned. Remove and set aside.

Sauté the Onions: In the same skillet, add the remaining vegetable oil, add sliced onion and sauté for 1 minute.

Add Aromatics: Add minced garlic and grated ginger, stirring for about 30 seconds until fragrant.

Stir-Fry the Cabbage: Add shredded cabbage and stir-fry for about 2–3 minutes or until slightly wilted.

Combine Beef and Sauce: Return cooked beef to the pan with cabbage, add sauce mixture and stir together.

Season to Taste: Sprinkle with salt and black pepper, stirring to combine. Adjust seasoning as needed.

Garnish and Serve: Transfer to a serving plate and garnish with sliced green onions or sesame seeds if desired.