Cut the pork into bite-sized pieces.
Thinly slice the onion, green onion, and garlic.
Make a marinade sauce by mixing gochujang (Korean chili paste), soy sauce, chili powder, sugar, sesame oil, minced garlic, and black pepper.
Mix the pork with the marinade and let it sit for 10 minutes.
Add oil to a pan and stir-fry the pork.
Add the onion and green onion, and stir-fry together.
Continue cooking over medium heat until the meat is fully cooked.