Something for the omnivores! Pork is the most popular meat in Japanese cooking, but so far I haven’t posted any (non-bacon) pork recipes on Just Bento, though I do have a couple over on Just Hungry that are bento-friendly, such as tonkatsu  (breaded and fried pork cutlets). This classic sweet-salty, intensely flavored miso marinated pork is really well suited to bentos. It is similar to miso chicken , but a bit more complex in flavor.
This makes enough for 2 to 3 bentos.
Time required: 5-10 minutes to marinade, some hours (up to 24) to marinate, and 5-8 minutes to cook.
If your pork cutlets are too thick (they should be about 5mm / about 1/5th of an inch thick), pound them out a bit with the side of a heavy knife or a meat tenderizer until they are thin enough.
Put all the ingredients except for the pork in a plastic ziplock bag. Mix the ingredients together by massaging the bag with your hands.
Put the pork cutlets in the bag, and close the bag up, expelling as much air as you can when you do so. Then, massage the marinade over the pork so that the pork is completely covered. See the photos below.
(Note: I’m using a method that keeps the hands as clean as possible, since the miso marinade is a bit messy. Of course if you object to the use of plastic bags, you can combine the marinade in a bowl or other container, then spread it over the pork with a spoon and your fingers.)
Make sure the bag is completely closed, and leave the meat to marinate for several hours or overnight. You should not marinate it much more than 24 hours though, or the salt in the miso will draw out the moisture of the pork too much and make it very dry.
When you are ready to cook the pork, pull them out of the bag, squeezing off as much of the miso as you can. The meat will have turned dark and rather transculent.
For bentos, cut the meat into bitesized pieces, and fry in a frying pan with just a little oil over medium heat for just 2-3 minutes or so on each side. Watch the meat so that it doesn’t burn (the miso on the surface may turn a bit black, but that’s ok.) When done, it should be cooked through but still juicy, and the surface should be a burnished brown.
Freezing: Put it in the freezer as soon as you put the meat into the miso marinade. The freezing process seems to retard the penetration of the marinade, so that it doesn’t draw too much moisture out of the meat. Thaw the meat marinade and all in the refrigerator the day before you intend to use it. You may want to freeze individual cutlets wrapped separately, so that you can pull out just as many as you need at a time.
If you don’t want to deal with messy miso in the morning, you can squeeze the meat out of the miso-marinade bag the night before,and keep it covered on a plate ready to just cook in a frying pan.
As I noted at the top of this article, pork is the most popular meat (not including poultry) in Japan, far more so than beef. In the town where my mother grew up, which is only about an hour from central Tokyo in Saitama prefecture, the local butcher didn’t sell beef until sometime in the 1980s, but he always had pork. (Lamb, goat and so on are barely known in Japan except as imports.) Pork even has a reputation for being quite healthy, since it contains the B-family of vitamins as well as plenty of collagen (which is supposed to keep your skin looking young.) The further south you go, the more popular pork is. Okinawan cuisine features pork very prominently.