Slice the flank steak thinly against the grain and set aside. Wash and cut the broccoli into florets. Mince the garlic and ginger.
In a small bowl, whisk together the soy sauce, oyster sauce, cornstarch, sugar, and beef broth until smooth. Set aside.
Heat a large skillet or wok over medium-high heat and add 1 tablespoon of vegetable oil. Once hot, add the sliced beef. Stir-fry for about 2-3 minutes until the beef is browned. Remove it from the skillet and set aside.
In the same skillet, add the remaining tablespoon of vegetable oil. Add minced garlic and ginger, stir for about 30 seconds until fragrant.
Add the broccoli florets to the skillet and stir-fry for about 3 minutes until they are tender but still crisp.
Return the cooked beef to the skillet with the broccoli. Pour the sauce mixture over the beef and broccoli. Stir well to coat everything evenly.
Continue to cook for another 2-3 minutes until the sauce thickens.
Serve the beef and broccoli hot over cooked rice.