This casserole is simple and delicious, and makes a perfect snack during a picnic (bento anyone?)—you should use it as a basic idea for a casserole, since the pasta sauce is the stable and the most important piece of the meal. It's also a very tweak-able recipe! :-)
The bare tuna-paste bento was a great success, but with the arrival of my new bento container, I was left with some extra unused space. I decided to fill the space with easy to make and very tasty iri tamago, which is basically a Japanese kind of scrambled eggs! You can definitely use iri tamago in onigiri, or as a small side dish.