In a mixing bowl, whisk together the beaten egg, sliced flank steak, finely grated ginger, peanut oil, and a pinch of salt. Cover with plastic wrap and let it marinate for 15-20 minutes.

In a separate bowl, combine the broth, Shaoxing wine, soy sauce, Chinkiang vinegar, sugar, cumin powder, and cornstarch. Whisk until smooth.

Heat a skillet or wok over medium-high heat and add a splash of peanut oil. Coat the marinated beef with cornstarch and cook in a single layer for 2-3 minutes. Flip and sear for another 1-2 minutes, then remove and set aside.

In the same skillet, sauté the chopped green onions, ginger slices, and minced garlic for about 30 seconds. Add the bell pepper and baby bok choy, stirring quickly for 1 minute.

Stir in the prepared sauce and cook for 2-3 minutes until it thickens. Return the beef to the skillet and mix well.

Serve hot over steamed rice or rice noodles. Garnish with roasted sesame seeds if desired.