Cut chicken tenderloin into bite-sized pieces.
Julienne the onion and green onion.
Heat cooking oil in a pan and stir-fry the green onion to release its aroma.
Add the chicken tenderloin and cook over high heat.
Add the onion and stir-fry.
Season with soy sauce, cooking wine, and sugar.
Lower the heat and stir-fry until the sauce is well absorbed.
Finish with sesame oil and black pepper.