Do not go to the comments and start yelling yet.
Now. OK. This has been bugging me all year, ever since Bon Appetit weighed in on the subject of reheating pizza in a skillet with its own (now more than half-broken) slideshow of advice. On the question of leftover fish, the expert advice was:
The only thing worse than eggs when reheated? Fish. Just don't do it. Firmer fish like salmon and bluefish are good when eaten cold, or flaked and tossed into a salad. Otherwise, just feed it to your pet.
This is wrong, destructive advice. It is true that unlike pizza, which is sometimes improved on reheating, fish is never going to be better than it was when you first cooked it. It is also true that it is very easy to ruin fish while reheating it.
But sometimes you do have leftover fish. It is not easy to calibrate portions of fish. Often when you purchase fish, you do it by the individual fish, which is a nonstandard unit of measure. Moreover, if you are cooking fish for children, sometimes they will eat it voraciously and sometimes they will not.
So in practice, the alternative to having leftover fish is to sometimes have not enough fish, and to realize this in mid-meal, and to start scanting your own portions to cover for your miscalculation. Better to err on the side of oversupply.
Here, then, is what you do with the remaining portion of fish. The next day—and no later, this isn't magic—put it in a microwaveable dish and cover it, and put the dish in the microwave.
Then comes the part that is annoying, but not as annoying as some magazine writer telling you to give up and feed a tasty and relatively expensive chunk of protein to your pet, when you don't even have a pet: Microwave it for 20 seconds, with the power on 30 or 40 percent. No more. Check it. It will be indistinguishable from how it was when you took it out of the fridge.
Rearrange it in the dish a little. Microwave it again, maybe only 15 seconds, again at no more than 40 percent. Check it, repeat. Keep going.
It will be slow. But at some point, after you've done this several times, the fish will be just warm when you check it. The texture will be more or less what it was when it came out of the fridge. You're done.
Eat the judiciously warmed-up fish. If you are eating it over rice, you can make the rice nice and hot, and you can stop warming the fish as soon as the chill is off it.
You can also do this with meat—30 or 40 percent power, in little bursts, till it's just warm. (You might even be able to do it with eggs.) It's boring, and it's much more labor-intensive than you expect using a microwave to be. But you also expect your microwave to rubberize your leftovers. It doesn't necessarily have to.
[Illustration by Tara Jacoby]