Cut the pork neck into bite-sized pieces.
Mix soy sauce, minced garlic, sugar, pepper, and sesame oil to make the marinade.
Add the pork neck to the marinade and let it sit for 30 minutes.
Heat a pan over medium heat and add cooking oil.
Place the marinated pork neck in the pan and grill until both sides are golden brown.
Add onion and green onion, stir-frying together.
Transfer to a plate and serve.