Begin by slicing the beef against the grain into thin strips about 1/4 inch thick. In a bowl, combine the beef strips with soy sauce, oyster sauce, and a bit of baking soda if desired, allowing it to marinate for 15-20 minutes.

Heat 1 tablespoon of vegetable oil in a large wok or skillet over high heat until it shimmers, about 1-2 minutes.

Carefully add the marinated beef in small batches, cooking for 1-2 minutes undisturbed until browned, then set aside.

In the same pan, add the remaining tablespoon of oil, then toss in the sliced onions. Stir-fry for 2-3 minutes until lightly caramelized.

Add the minced garlic to the pan and stir constantly for about 30 seconds, being cautious not to burn it.

Return the seared beef to the pan with the onions, add any remaining marinade, and stir to combine for another 1-2 minutes.

Taste and adjust seasoning with salt and pepper. Garnish with chopped green onions and serve immediately.