Slice the pork thinly.
Chop the onion, green onion, and garlic.
Make the marinade with gochujang (Korean chili paste), soy sauce, sugar, minced garlic, and gochugaru (chili powder).
Mix the pork with the marinade thoroughly.
Heat oil in a pan, then stir-fry the pork and vegetables together.
When cooked through, transfer to a plate.