Cut the chicken tenderloin into bite-sized pieces.
Slice the onion and green onion.
Heat cooking oil in a pan and stir-fry the chicken tenderloin.
Add soy sauce, sugar, and minced garlic to the chicken and mix.
Add onion and green onion, then stir-fry together.
Season with black pepper.
Turn off the heat and finish with a drizzle of sesame oil.