Saba nitsuke is an exquisite little simmered-dish (nimono) that benefits from top-quality mackerel (we get ours from Fin & Flounder in Broadway Market and, touch wood, haven’t had a Sancho Panza-style gushing-from-both-ends bout of food poisoning yet).
Scale, gut and wash 2 mackerel, or get the fishmonger to do it (ideally they take out the little “pin” or “fin” bones but it doesn’t matter as they’re not terribly hard). This recipe is sized for about 400g of mackerel fillets.
Heat about 175ml of cooking sake in a pan slightly deeper than the one in these pictures, yet wide enough to take the fillets. When simmering, place the mackerel skin-side up. Turn up the heat to a rapid boil. Add 100ml of mirin, and let it get back to a boil. Add 80ml of soy sauce, again let it boil. Finally grate 30ml of ginger over the fish, and a tiny amount of sugar. This “staggered boiling” process is what gets rid of any fishy odour the mackerel might have.
Now put on a “drop-lid” (otoshi-buta) or (since they’re hard to find) simply a piece of foil with a hole in the middle, that fits into the pot reasonably well (hence I’d suggest a pot slightly deeper than the one I used, as the liquid tends to boil over). This allows for the fish to cook briskly, without the movement that would cause it to break up.
Cook on high heat for 8-10 minutes, check for doneness, and serve hot. The dish tends to be quite strongly flavoured / salty, so it’s good to serve with steamed white rice and simple boiled spinach.