Rinse the mackerel pieces under cold water and pat them dry with paper towels. Score the thickest parts of the fish with a few diagonal cuts.
2
Prepare the braising sauce by combining gochujang, gochugaru, soy sauce (ganjang), mirin, sugar, minced garlic, minced ginger, and black pepper in a bowl. Mix well until all ingredients are thoroughly combined.
3
Arrange the sliced Korean radish (mu) evenly on the bottom of a large, shallow pot or deep pan. This prevents the mackerel from sticking and infuses the radish with flavor.
