Cut the chicken into bite-sized pieces.
Chop the onion, green onion, and garlic.
Make the sauce by mixing gochujang, soy sauce, sugar, sesame oil, and minced garlic.
Heat oil in a pan and stir-fry the chicken.
Add onion, green onion, and the sauce, then stir-fry together.
Once the chicken is fully cooked, transfer to a plate and serve.