Slice the beef thinly.
Make the marinade with soy sauce, sugar, minced garlic, sesame oil, and pepper.
Add the marinade to the beef and let it marinate for 20 minutes.
Julienne the onion, carrot, and green onion.
Heat oil in a pan and stir-fry the onion, carrot, and green onion.
Add the marinated beef and stir-fry over high heat.
Sprinkle sesame seeds on top when cooked to finish.