Slice the beef thinly.
Julienne the onion, green onion, and carrot.
Make the marinade using soy sauce, sugar, minced garlic, sesame oil, and pepper.
Add the marinade to the beef and let it sit.
Heat cooking oil in a pan and stir-fry the onion and carrot.
Add the marinated beef and stir-fry.
Add the green onion and continue to stir-fry until cooked.