Begin by slicing flank steak thinly against the grain, then combine it with soy sauce and cornstarch in a bowl. Let it marinate for about 10 minutes.

In a large pot, bring water to a rolling boil. Blanch the broccoli florets for 2 minutes until bright green. Drain and plunge into ice water.

Heat 2 tablespoons of vegetable oil in a large skillet over medium-high heat until shimmering.

Add marinated beef to the skillet in a single layer, stir-fry for 2-3 minutes until browned, then remove and set aside.

In the same skillet, add minced garlic and ginger. Stir-fry for 30 seconds until fragrant.

Return the cooked beef and blanched broccoli to the skillet. Pour in soy sauce, oyster sauce, and beef broth, then mix well.

Reduce heat to medium and let the mixture simmer for 2-3 minutes to thicken the sauce.

Taste and adjust seasoning with salt and pepper if needed before serving hot over steamed rice or noodles.