Follow these steps to create your delicious Chinese Beef and Broccoli:

1. Prepare the Beef: Thinly slice the flank steak or sirloin against the grain for tenderness. Set aside.
2. Marinate: In a bowl, mix the soy sauce, oyster sauce, and cornstarch. Add the sliced beef and toss well to coat. Let it marinate for about 10 minutes.
3. Heat the Oil: In a large skillet or wok, heat the vegetable oil over medium-high heat until shimmering.
4. Cook the Beef: Add the marinated beef to the hot skillet. Stir-fry for 3-4 minutes until it’s browned and cooked through. Remove the beef from the skillet and set aside.
5. Sauté the Garlic: In the same skillet, add minced garlic and stir-fry for about 30 seconds or until fragrant.
6. Add the Broccoli: Add the broccoli florets. Stir-fry for 3-4 minutes, adding a splash of water if necessary to steam and cook the broccoli until tender-crisp.
7. Combine Ingredients: Return the cooked beef to the skillet with the broccoli. Stir everything together and let it cook for another 2 minutes to heat through.
8. Serve: Taste and adjust seasoning if needed, then remove from heat.