Cut the pork into bite-sized pieces.
Slice the onion, green onion, and chili peppers.
In a bowl, mix gochujang, soy sauce, sugar, minced garlic, chili powder, and sesame oil to make the sauce.
Add the sauce to the pork, mix well, and marinate for 10 minutes.
Heat oil in a pan and stir-fry green onion to bring out its aroma.
Add the pork and stir-fry over high heat.
When the pork is cooked, add onion and chili peppers, and continue stir-frying.
When all ingredients are cooked through, sprinkle sesame seeds on top to finish.