Cut the pork into bite-sized pieces.
Slice the onion and green onion.
Make the sauce by mixing gochujang, soy sauce, minced garlic, sugar, and gochugaru (Korean red pepper flakes).
Add the sauce to the pork and mix well.
Heat oil in a pan and stir-fry the green onion to bring out the aroma.
Add the pork and onion, then stir-fry together.
Once the pork is cooked through, transfer to a plate.