Add baking soda and water to the sliced beef and massage with hands until most of the liquid is absorbed. Let stand 1-2 hours.
Rinse the beef thoroughly under running water until the water runs clear. Drain.
Add oil, oyster sauce/soy sauce, Shaoxing wine (optional), and cornstarch to the beef. Set aside to marinate for 15-30 minutes, and then your beef is ready to use.
Video
Notes
Short-Cut Method for Tenderizing Beef: Add 1/8 teaspoon to 1/4 teaspoon (for tougher cuts) of baking soda and 2-3 tablespoons of water to the beef. Add remaining marinade ingredients. Mix, and marinate for 30 minutes, up to overnight.