Creating Beef and Broccoli Stir Fry is straightforward if you follow these steps:

1. Prep the Beef: Thinly slice the beef sirloin against the grain for tenderness.
2. Marinate: In a bowl, combine the soy sauce, oyster sauce, cornstarch, and black pepper. Add the sliced beef and mix well. Let it marinate for about 10 minutes.
3. Prepare the Broccoli: While the beef marinates, rinse and cut the broccoli into florets.
4. Heat the Oil: In a large skillet or wok, heat the vegetable oil over medium-high heat.
5. Cook the Beef: Add the marinated beef to the skillet in a single layer. Sear for 2-3 minutes without stirring to achieve a good browning. Then, stir-fry until the beef is cooked through, about 2-3 more minutes. Remove the beef from the skillet and set aside.
6. Stir-Fry the Broccoli: In the same skillet, add a bit more oil if needed. Add the broccoli florets and stir-fry for about 3-4 minutes until bright green and tender-crisp.
7. Add Aromatics: Stir in the minced garlic and ginger, cooking for an additional 30 seconds until fragrant.
8. Combine: Return the cooked beef to the skillet with the broccoli. Mix everything together and drizzle with sesame oil if desired.
9. Serve: Remove from heat and serve immediately over cooked rice.

These steps will guide you in creating this incredible dish effortlessly.