Combine beef slices with cornstarch, 1 tablespoon oil, water, oyster sauce, and baking soda. Mix well and marinate for 20 minutes.

Prepare the sauce by whisking together light soy sauce, dark soy sauce, oyster sauce, sesame oil, sugar, and warm water. Set aside.

Heat 1 tablespoon oil in a wok over high heat. Sear the beef in a single layer for about 1 minute per side until browned but still slightly pink inside. Transfer to a plate.

Add remaining oil. Stir-fry garlic and ginger for 10 seconds until fragrant. Add bok choy stems and mushrooms, cooking for 2 minutes. Add snap peas and bok choy leaves, stir-frying another minute.

Return beef to the wok. Pour in the sauce and toss everything together over high heat for 30 seconds until the sauce thickens and coats all ingredients.

Serve immediately over steamed jasmine rice.