Marinate the Beef:
In a bowl, combine the thinly sliced beef with 1 tablespoon of soy sauce, 1 tablespoon of cornstarch, and 1 tablespoon of sesame oil (optional).
Mix well and let it marinate for at least 20 minutes. This will help tenderize the beef and add flavor.
Prepare the Sauce:
In a small bowl, whisk together 1/4 cup soy sauce, 2 tablespoons oyster sauce, 1 tablespoon cornstarch, 1 teaspoon sugar, and 1/4 cup water or beef broth.
Stir in the minced garlic and ginger. Set aside.
Cook the Beef:
Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat.
Add the marinated beef to the skillet and cook for 2-3 minutes until browned, stirring occasionally.
Once cooked, remove the beef from the skillet and set it aside.
Stir-Fry the Broccoli:
In the same skillet, add the broccoli florets and 1/4 cup of water.
Cover the skillet and let the broccoli steam for 2-3 minutes until bright green and slightly tender.
Remove the lid and stir-fry the broccoli for an additional minute until crisp-tender. If needed, add a little more oil for stir-frying.
Combine the Beef, Broccoli, and Sauce:
Return the cooked beef to the skillet with the broccoli.
Pour the prepared sauce over the beef and broccoli, stirring to combine.
Cook for another 2-3 minutes until the sauce thickens and evenly coats the beef and broccoli.
Serve:
Remove from heat and serve hot over steamed rice or noodles.
Garnish with sesame seeds and sliced green onions if desired.