Cut your cleaned mackerel into medium-sized sections (cut each piece about to the second crease in your pinky finger - reference video).
Peel the Korean Radish. Cut into thin circles. Then cut each circle in half.
Cut Spring Onion pieces into thin slices.
Make Braising Sauce: Thoroughly mix Soy Sauce (4 Tablespoon), Gochugaru (1 Tablespoon), Gochujang (2 Tablespoon), Honey (2 Tablespoon), Mirim (2 Tablespoon), Garlic (1 teaspoon!) and Black Pepper (few shakes)
Take out a large pot. Add Korean Radish on the bottom. Then place the mackerel pieces on top. Then add spring onion pieces over the top.
Add in the Spicy Braising Sauce. Next, add in the water (1 cup) into your marinade bowl and wash out the remainder into your pot.
Put the pot on medium-high heat. Place lid on. Bring up to a boil.
After it comes to boil, we'll reduce it for 20-25 minutes (with the lid on) (Note: 10 minutes in, open the lid and make sure the fish pieces are submerged into the sauce as well)
After 20-25 minutes, the broth will have reduced into a small layer of sauce. You'll see large bubbles form at the bottom of the pot (reference video). Now, turn the heat off.
Plate and enjoy with a bowl of hot rice!