In a bowl, combine the beaten egg, thinly sliced flank steak, finely grated ginger, peanut oil, and salt. Mix well and let it stand at room temperature for 15-20 minutes.

Whisk together the broth, Shaoxing wine, soy sauce, Chinkiang vinegar, sugar, cumin powder, and cornstarch in a separate bowl. Set aside.

Sprinkle cornstarch over the marinated beef and stir until evenly coated.

Heat a large skillet or wok over medium-high heat. Add peanut oil and add beef in a single layer. Sear for 2-3 minutes, then flip to brown for an additional 1-2 minutes. Remove and set aside.

In the same skillet, add green onions, ginger, and garlic. Stir quickly for 30 seconds, then add bell peppers and bok choy. Stir for 1 minute.

Pour the prepared sauce over vegetables, stirring until thickened (1-2 minutes). Return beef to skillet, toss to coat in sauce and remove from heat.

Serve hot over steamed rice, garnished with sesame seeds and extra green onions.