Prepare and Velvet the Beef: In a medium bowl, combine the thinly sliced flank steak with 1 tablespoon of soy sauce and 1 tablespoon of cornstarch. Use your hands to toss until every piece is lightly coated. Set aside to marinate for at least 15 minutes.

Whisk Together the Sauce: While the beef marinates, prepare the sauce. In a small bowl or liquid measuring cup, whisk together 3 tablespoons of soy sauce, beef broth, oyster sauce, Shaoxing wine, brown sugar, and the remaining 1 teaspoon of cornstarch until the cornstarch is fully dissolved. Set aside.

Sear the Beef: Heat a large skillet or wok over high heat until very hot. Add 1 tablespoon of oil. Once shimmering, add the beef in a single layer, working in batches if necessary to avoid overcrowding. Sear for 60-90 seconds per side until nicely browned but not fully cooked. Remove the beef from the skillet and set aside on a plate.

Sauté Aromatics and Cabbage: Reduce the heat to medium-high and add the remaining tablespoon of oil to the skillet. Add the minced garlic and ginger and stir-fry for about 30 seconds until fragrant. Add the sliced cabbage and the white parts of the scallions. Toss continuously for 4-5 minutes, until the cabbage is wilted but still crisp-tender.

Combine and Thicken: Return the seared beef to the skillet with the cabbage. Give the sauce a final whisk and pour it over everything. Stir to combine and let it simmer for 1-2 minutes, until the sauce thickens to a glossy consistency that coats the ingredients.

Finish and Serve: Turn off the heat. Stir in the toasted sesame oil and the green parts of the scallions. Serve immediately over steamed rice, garnished with extra scallions or toasted sesame seeds if desired.