Marinate the Beef: In a bowl, combine the thinly sliced beef with grated ginger, minced garlic, soy sauce, and sesame oil. Toss well to ensure the beef is evenly coated with the marinade. Let it marinate for at least 15-30 minutes.
Blanch the Broccoli: Bring a pot of water to a boil. Add the broccoli florets and blanch for about 2 minutes, until they are bright green and slightly tender. Remove the broccoli from the boiling water and immediately rinse it under cold water to stop the cooking process. Set aside.
Prepare the Sauce: In a small bowl, mix together the cornstarch and water to create a slurry. This will thicken the sauce later on.
Cook the Beef: Heat a large skillet or wok over medium-high heat. Spray oil on the pan. Once the oil is hot, add the marinated beef to the skillet in a single layer. Cook for 2-3 minutes without stirring, allowing the beef to sear and brown on one side. Then, stir-fry for an additional 1-2 minutes until the beef is cooked through. Remove the beef from the skillet and set aside.
Make the Sauce: In the same skillet or wok, add a little more oil if needed. Add the grated ginger and minced garlic, and stir-fry for about 30 seconds until fragrant. Pour in the soy sauce and bring it to a simmer. Then, add the cornstarch slurry to the skillet, stirring continuously until the sauce thickens and becomes glossy.
Combine Beef and Broccoli: Return the cooked beef to the skillet, along with the blanched broccoli florets. Toss everything together until the beef and broccoli are evenly coated with the sauce. Cook for an additional 1-2 minutes until heated through.
Serve: Transfer the Beef and Broccoli to a serving dish and serve hot. You can enjoy it as is or serve it over steamed rice or noodles for a complete meal. Enjoy!