Marinate the beef slices in soy sauce and cornstarch for about 10 minutes.
Heat vegetable oil in a large skillet or wok over medium-high heat.
Add minced garlic and ginger, sauté for 30 seconds until fragrant.
Add the marinated beef to the skillet and stir-fry until browned, about 3-4 minutes.
Remove the beef from the skillet and set aside.
Add broccoli florets to the skillet and stir-fry for 2-3 minutes.
Pour in the beef broth and cover to steam the broccoli for about 2 minutes.
Uncover, return the beef to the pan, and add oyster sauce.
Stir everything together and cook for an additional 2-3 minutes.
Adjust seasoning with salt and pepper, then serve hot.