In a large bowl, combine thinly sliced beef flank steak with baking soda, light soy sauce, peanut oil, and cornstarch. Mix well, ensuring each piece is evenly coated. Let the beef marinate for at least 15 minutes.

In a small bowl, whisk together chicken broth, oyster sauce, dark soy sauce, sugar, cornstarch, and sesame oil until well combined. Set the sauce mixture aside.

Heat 1 tablespoon of peanut oil in a large skillet or wok over medium-high heat. Add the marinated beef in a single layer, cooking for about 1 minute until golden brown on one side. Flip the beef and cook for another minute until just done. Remove beef and keep warm.

In the same skillet, add the remaining tablespoon of oil. Add sliced onion, minced garlic, and grated ginger, stirring for about 2 minutes until fragrant. Add asparagus or your choice of vegetables, stir-frying until bright and just tender, about 1 minute.

Stir the sauce mixture and pour it into the skillet. Cook for another minute until the sauce thickens and coats the vegetables. Return the cooked beef, tossing everything together.

Plate the Beef with Oyster Sauce, garnish with sesame seeds if desired, and serve hot over steamed rice.