Combine all sauce ingredients -- soy sauce, dark soy sauce, oyster sauce, sesame oil, sugar, water, cracked black pepper, and MSG if using. Whisk together and set aside.
Toss steak cubes with light soy sauce, baking soda, sugar, cornstarch, cracked black pepper, and sesame oil. Mix well and marinate for 20-60 minutes.
Heat 1 tablespoon of oil in a wok over high heat until smoking. Add the steak in a single layer and sear until browned on the outside and just cooked through. Do not overcrowd. Remove and set aside.
Reduce heat to medium. Add butter, garlic, shallot, and the white parts of the green onion. Sauté for 30-45 seconds until fragrant. Pour in the beaten eggs and scramble gently until just set. Push to one side of the pan.
Add the frozen mixed vegetables and stir-fry for 1-2 minutes until heated through. Add the cold rice, breaking up any clumps. Crank the heat to high and stir-fry everything together for 2-3 minutes until the rice is slightly toasted.
Add the green parts of the green onion, the seared steak, and the pre-mixed sauce. Toss everything together until evenly coated and heated through. Taste and adjust with extra soy sauce or cracked black pepper. Serve hot.