Put the mackerel fillets in a large frying pan.
Add all the ingredients except miso and bring to a boil.
Let the sauce reduce on medium heat. Progressively cover the fillets with sauce and cook for an additional 6 minutes.
Put miso in a bowl, add a few spoonfuls of sauce and stir well to make a homogeneous base. Pour in the frying pan and let simmer the fish with sauce for 10 minutes.
Drizzle the fillets with sauce and serve with japanese rice and a few coriander leaves.