Mix gochujang, soy sauce, rice wine, sugar, minced garlic, and red pepper powder in equal portions (5 tbsp each) to create the seasoning sauce.

Prepare the pork belly and bean sprouts. Rinse the bean sprouts under running water and drain thoroughly.

Slice the perilla leaves and green onion into bite-sized pieces. Thinly slice the onion and king oyster mushroom.

Layer bean sprouts at the bottom of a deep stir-fry pan, followed by the pork belly slices.

Add the onion, king oyster mushroom, and most of the prepared seasoning sauce (about 4/5 of it). Stir-fry everything together, adding more sauce as needed.

Once the pork is mostly cooked, add the perilla leaves and green onion. Lightly mix and cook for a few more minutes.