1Slice the beef sirloin into thin strips.
In a bowl, mix the beef strips with 1 tbsp of cornstarch, 1 tsp of salt, and 1 tsp of black pepper. Set aside.
Cut the broccoli into bite-sized florets.
Mince the garlic and grate the ginger.
Heat a large pan or wok over medium-high heat and add a bit of oil.
Add the beef strips to the pan and stir-fry until browned and cooked through. Remove the beef from the pan and set aside.
In the same pan, add the minced garlic and grated ginger. Stir-fry for about 30 seconds until fragrant.
Add the broccoli florets to the pan and stir-fry for about 3-4 minutes until they are tender-crisp.
Return the beef to the pan and add the soy sauce, oyster sauce, and red pepper flakes. Stir well to combine all the ingredients.
Cook for another 2-3 minutes until everything is heated through and the sauce has thickened slightly.
Serve hot with steamed rice or noodles.