Follow these simple steps to create your Beef & Onion Stir-Fry with ease:

1. Prep the Beef: Slice the beef into thin strips against the grain. This ensures tenderness.
2. Marinate the Beef: In a bowl, mix the sliced beef with soy sauce, oyster sauce, cornstarch, and a pinch of salt. Let it marinate for at least 15 minutes.
3. Prepare the Vegetables: While the beef marinates, slice the onions and mince the garlic and ginger (if using).
4. Heat the Skillet: In a large skillet or wok, heat the vegetable oil over medium-high heat.
5. Cook the Beef: Add the marinated beef to the skillet in a single layer. Sear for 1-2 minutes until browned, then stir-fry for another 2-3 minutes until fully cooked. Remove the beef from the skillet and set aside.
6. Stir-Fry the Onions: In the same skillet, add a bit more oil if necessary, then add the sliced onions. Stir-fry for 3-4 minutes until they are translucent and slightly caramelized.
7. Add Garlic and Ginger: Stir in the minced garlic and ginger. Cook for an additional minute until fragrant.
8. Combine Ingredients: Return the cooked beef to the skillet with the onions. Drizzle sesame oil over the mixture and stir everything together.
9. Final Seasoning: Taste and adjust seasoning with salt, pepper, or additional soy sauce if needed.
10. Garnish: Remove from heat and sprinkle sliced green onions on top for a fresh touch.