Put the block of pork belly and sliced (5 mm) ginger into a pressure cooker. Add enough water to cover the pork and 1/2 cup (100 ml) of sake.
Lock the lid on the pressure cooker and turn the heat on to high. When it's reached pressure, turn the heat down to low and cook for 15 minutes. Turn the heat off and leave to rest for 5 minutes.
After 5 minutes, press down the pressure valve to release steam and remove the lid. Throw away the boiling liquid, and rinse the pork in lukewarm water. Cut into bite sized pieces. Wash the pressure cooker, too.
Put the cubed pork and the ☆ ingredients into the pressure cooker, and lock the lid again.
Turn the heat on to high. When it's reached pressure, turn the heat down to low and cook for 5 minutes. Turn the heat off and leave to rest for 5 minutes. Press the valve to release steam, and remove the lid.
Add peeled soft boiled eggs, and simmer while turning the pork over medium heat for about 5 minutes. Done!
How to cook soft boiled eggs: Put the eggs carefully into boiling water, and cook for 6.5 minutes. Drain, cool in ice cold water, and they're done. You can use eggs straight out of the refrigerator.
The bento also has : Onigiri rice balls wrapped in nozawana (pickled green leaves), cucumbers wrapped in salted squid, shimeji mushrooms and broccoli mixed with umeboshi plum and shiro-dashi sauce, and sauteed kabocha squash.
Story Behind this Recipe
I made the usual simmered pork belly cubes (buta no kakuni) with Shinshuu miso from the region I'm from. I used pork from Shinshuu Miyuki pigs. Regarding the squid rolls that I put into the bento - in landlocked Nagano prefecture (formerly the Shinshuu region) we have something called "shio maru ika", which is salt-cured squid. It's a regional speciality that we've had since the olden days, when we couldn't get fresh seafood. The usual way to eat it is to chop it up and mix it with other things.
Combine the flavoring ingredients beforehand in a bowl. This makes it easier to work, and the flavors will be right too. By simmering the ingredients with the lid off after cooking them under pressure, the flavors will be distributed evenly.