Remove the head and innards from the fish and chop into 3 pieces.
Wash well with cold water, especially the blood near the spinal bone.
Make a cross cut on the skin.
Place in a colander and pour hot water in circular motion.
Put the ● ingredients into a pot and heat. Once boiled, add the fish and avoid overlapping the pieces. Make a "drop lid" by cutting parchment paper the same size of the pot and lay on top of the fish. Simmer for 5 minutes in medium heat.
Dissolve the miso, oyster sauce, and sesame oil and cook for 15 minutes. Spoon the broth over the fish occasionally.
When the broth has reduced by 2/3 and it has become thick and starchy, it's done.
Story Behind this Recipe
A friend advised me to add sesame oil to miso simmered mackerel, and I've been doing so ever since.
If the fish is small, cut into half. As there is very little broth to begin with, do not over boil. If you over-boil, the fish will become too salty.