Prepare the vegetables. You can substitute cabbage or mushrooms if desired. Mix gochujang, chili powder, sugar, sesame oil, and black pepper to make the sauce. Adjust soy sauce to taste before serving.

Heat 1 tbsp chili oil in a pan. Add onion, chicken breast, and the prepared sauce. If chili oil is unavailable, mix 1/2 tbsp chili powder with 1 tbsp sesame oil in the pan as a substitute.

Once the sauce is well mixed and the onion turns slightly translucent, add green onion and green chili pepper. For a saucier dish, add 3–5 tbsp water to the sauce.

Briefly stir-fry after adding green onion and chili pepper.

Serve the mixture over warm rice.