In a small bowl, whisk together beef broth, soy sauce, oyster sauce, sesame oil, and cornstarch for the sauce. Set aside.
Heat vegetable oil in a large skillet or wok over medium-high heat. Add flank steak and cook until browned, about 2-3 minutes. Remove steak from skillet and set aside.
Add broccoli florets to the skillet and stir-fry for 3-4 minutes until tender-crisp. Add minced garlic and ginger and cook for another minute until fragrant.
Return the cooked beef to the skillet. Pour the prepared sauce over the beef and broccoli. Stir and cook until the sauce has thickened, about 1-2 minutes.
Cook ramen noodles according to package directions, omitting the seasoning packets. Drain well.
Add the drained ramen noodles to the skillet with the beef and broccoli mixture. Toss to combine and ensure noodles are coated with the sauce.
Serve immediately.
Notes
Garnish with sesame seeds and chopped green onions if desired.