Cut the sliced beef brisket into bite-sized pieces.
Slice the onion, green onion, and Cheongyang chili pepper.
Heat oil in a pan and stir-fry the beef brisket.
When the meat is half cooked, add the vegetables and continue stir-frying.
Add gochujang (Korean red chili paste), soy sauce, sugar, minced garlic, and sesame oil, mixing everything evenly.
Continue stir-frying until all ingredients are fully cooked.