Place green onions on top of the pork belly and slice them together into bite-sized pieces.

Place the sliced pork and green onions in a microwave-safe container. Add sliced king oyster mushrooms and garlic cloves.

Pour a mixture of soy sauce, mirin, and water in a 1:1:1 ratio over the ingredients. Sprinkle with pepper.

Cover the container and microwave for 10 minutes. It's recommended to pause halfway through to check. If it's not fully cooked, microwave for additional time.

In a small bowl, combine doenjang, gochujang, mayonnaise, oligosaccharide, minced garlic, chopped chili pepper, sesame oil, and sesame seeds. Mix well.

Serve the cooked pork belly warm with the Doenjang mayo sauce for dipping.