Instructions:
- Slice the steak thinly against the grain (about 1/8 inch thick) and place it in a bowl.
- Velvet the Beef: Add the egg white, 1 Tbsp soy sauce, rice wine, cornstarch, baking soda (if using), and 1 Tbsp vegetable oil to the beef. Mix thoroughly until sticky, then set aside to marinate for at least 15 minutes.
- Prepare the Sauce: In a separate bowl, whisk together the beef broth, 3 Tbsp soy sauce, brown sugar, oyster sauce, black vinegar, 1 Tbsp cornstarch, and black pepper until the cornstarch is fully dissolved. Set aside.
- Prep Vegetables: Chop the onion and green peppers into uniform pieces. Mince the garlic and ginger.
- Sear the Beef: Heat 2 Tbsp of vegetable oil in a large wok or heavy skillet over high heat until shimmering. Add the marinated beef in a single layer (work in batches if necessary) and sear quickly for 1-2 minutes per side until edges are browned but still slightly pink inside. Remove the beef and set aside.
- Sauté Vegetables: Add the remaining 1 Tbsp of oil to the wok. Add the onions and peppers and stir-fry rapidly for 2-3 minutes until crisp-tender. Push the vegetables to one side.
- Bloom Aromatics: Add the minced garlic and ginger to the cleared space in the wok. Stir-fry for 30 seconds until fragrant, then toss them with the vegetables.
- Thicken Sauce: Give the prepared sauce a quick re-whisk and pour it into the centre of the wok. As it bubbles, it will thicken rapidly.
- Combine and Finish: Immediately return the seared beef to the wok. Toss everything vigorously for about 30 seconds to coat evenly in the glossy sauce, ensuring the beef is cooked through.
- Serve immediately after turning off the heat, drizzling with sesame oil and garnishing with sliced scallions.