Slice the pork thinly.
Cut the onion and green onion.
In a bowl, mix soy sauce, sugar, minced garlic, sesame oil, and black pepper to make the marinade.
Add the marinade to the pork and let it marinate for 20 minutes.
Add cooking oil to a pan and preheat over medium heat.
Stir-fry the onion and green onion, then add the pork.
Stir-fry over high heat until the pork is cooked through.
Finish by sprinkling sesame seeds.