Cut the chicken breast into bite-sized pieces.
Julienne the onion, green onion, and carrot.
Make the marinade sauce (soy sauce, gochujang, sugar, minced garlic, sesame oil, pepper).
Marinate the sliced chicken breast and vegetables in the sauce for 10 minutes.
Pour cooking oil into a pan and preheat over medium heat.
Add the marinated chicken breast and vegetables to the pan and stir-fry.
Continue stir-frying until the chicken breast is fully cooked.
Plate and sprinkle with sesame seeds to finish.