Thinly slice the pork shoulder. It's easier to cut when it's slightly frozen.
Prepare the bean sprouts and slice the onion.
In a small bowl, mix sugar, gochugaru, minced garlic, soy sauce, gochujang, and black pepper to make the sauce.
In a large pan, layer the sliced onion, bean sprouts, and pork in that order.
Pour the sauce over the pork.
Cover with a lid and cook on medium-high heat for 5 minutes. No water or oil needed — the moisture from the sprouts and onion will steam everything.
After 5 minutes, open the lid, stir everything well, and cook until the pork is fully done and evenly coated with sauce.
Serve hot over rice or wrapped in lettuce.
