Follow these simple steps to prepare an excellent Hunan Beef dish:

1. Prepare the Beef: Thinly slice the flank steak against the grain and season with salt, pepper, and cornstarch. Set aside.
2. Heat Oil: In a large skillet or wok, heat the vegetable oil over medium-high heat until shimmering.
3. Cook Beef: Add the sliced beef to the pan and stir-fry for about 2-3 minutes until browned and just cooked through. Remove from the pan and set aside.
4. Sauté Vegetables: In the same pan, add the onion, bell pepper, and broccoli. Stir-fry for 2-3 minutes until they are tender-crisp.
5. Add Garlic and Ginger: Stir in the minced garlic, ginger, and fresh chilies. Cook for another minute until fragrant.
6. Combine Ingredients: Return the beef to the pan and mix well with the vegetables.
7. Make Sauce: In a small bowl, combine soy sauce, Hunan chili paste, oyster sauce, and sugar. Pour this sauce over the beef and vegetables.
8. Stir Fry Together: Stir-fry everything together for an additional 2-3 minutes until cooked through and well combined.
9. Adjust Seasoning: Taste and adjust seasoning with salt, pepper, or more chili paste as needed.
10. Serve: Remove from heat and serve hot over cooked rice or noodles.

By following these steps, you’ll have an incredible Hunan Beef dish that is bursting with flavors and guaranteed to impress!