Prepare 2 medium sized fresh or frozen mackerel (750 grams, or 1.7 pounds). Thaw them out if frozen.
Cut off the fins and heads.
Make a slit from the top to the vent and clean the guts.
Cut the fish across into 2 inch pieces, rinse in cold water, drain, and set aside
Prepare your vegetables:
Peel a large, heavy Korean radish. Cut 1 kilogram (2.2 pounds) worth of radish into pieces 2 inch wide, 2 ½ inch long, and 1 inch thick.
Add the radish pieces to a large thick bottomed pot with. Spread them out evenly, by hand.
1 large onion or 2 medium sized onions (about 400 grams', or 2 cups' worth), cut into ¼ inch thick slices and place over the radish.
Cut 3 stalks of green onions into pieces 1 inch long, and chop 2 green chili peppers and 1 red chili pepper. Set aside
Let's make godeungeo jorim:
Place the mackerel on top of the pieces of radish.
Make seasoning sauce in a bowl by mixing ½ cup soy sauce, ¼ cup hot pepper flakes, 2 tbs sugar, ⅓ cup garlic cloves minced (12 cloves), and 1 tbs of minced ginger.
Pour the seasoning sauce over the fish. Pour in 1 cup of water along the edges of the pot.
Close the lid and bring to a boil over high heat for 20 minutes.
Open the lid, tilt the pot, and use a spoon to push aside the mackerel and radish to make empty spot for the broth to well.
Scoop some broth from the empty spot and pour it over top of the fish and radish. Repeat several times.
Add the chopped green onion, green and red chili peppers.
Close the lid and lower the heat to a simmer for 30-40 minutes, until the radish is cooked thoroughly. The radish will absorb the soy sauce based broth, so it will look brownish and a little translucent when cooked nicely.
Open the lid and turn up the heat to boil off excess broth.
Tilt the pot and use a spoon to push aside the mackerel and radish to make empty spot for the broth to well.
Scoop some broth from the empty spot and pour it over top of the fish and radish. Repeat it off and on for about 5-7 minutes.
Turn off the heat and transfer to a serving plate. Serve with rice, kimchi, soup, lettuce, and a few more side dishes.