Combine the pork, gochujang, soy sauce, brown sugar, garlic, ginger, and onion in a bowl.
Marinate the pork mixture for at least 30 minutes.
Heat a skillet or wok over high heat and add the marinated pork mixture.
Cook, stirring frequently, until the pork is cooked through and the sauce has thickened, about 5-7 minutes.
Drizzle with sesame oil and sprinkle with sesame seeds before serving.
