Steps
1. In a bowl, mix the beef slices with cornstarch, salt, and pepper. Let it marinate for 10 minutes.
2. Heat sesame oil in a pan over medium-high heat. Add the marinated beef and stir-fry until browned (about 3-4 minutes).
3. Add the garlic, onion, bell pepper, and broccoli to the pan. Stir-fry for an additional 5 minutes until the vegetables are tender.
4. Pour soy sauce over the stir-fry and toss everything to combine. Cook for another minute.
5. Serve hot over cooked rice if desired.