Cut the pork shoulder into bite-sized pieces.
Slice the onion, green onion, and garlic after prepping them.
In a bowl, mix together gochujang (Korean red chili paste), red pepper powder, soy sauce, minced garlic, sugar, sesame oil, and black pepper to make the marinade.
Add the marinade to the pork shoulder and let it marinate for 20 minutes.
Heat cooking oil in a pan, add the green onion, and make green onion oil.
Add the marinated pork and vegetables to the pan and stir-fry over high heat.
Once the pork is cooked through, transfer to a plate and serve.