One of the basic ingredients we use quite a bit of for New Year's Osechi-ryori is dashi. We use dashi to impart a key taste to many of the dishes we prepare for many different types of meals. The basic stock we make is based on katsuoboshi shaved into what essentially looks like wood shavings (at least to me, back to this later). We also add a little piece of kombu, a type of dried sea algae, often called kelp in the U.S. There are many forms and types of kombu, but, we use the sheets of the kombu leaves. This broth finds it's way into all of the soups, stews and some of the seasoned vegetables we prepare throughout the year.
Here is our pot or dashi being simmered.
From here, the katsuoboshi is removed, drained and discarded. The broth is allowed to cool and settle, which avoids filtering. The broth at this point is a building block of umami flavors. The kombu and katsuoboshi adding amino acids, salt, protein and complexity. We will end up adding this to eggs for tamagoyaki and sushi, sushi vegetables for makisushi, BBQ sauce (my own swing, he he), oden and soup. In fact, if you touch it up with some fish sauce and herbs, you have a great Pan-Asian soup base, I use it for a base in fried rice and noodle sauces, soba broth and dipping sauces.
I have experimented with it for adding a MSG effect to BBQ sauces that would otherwise not be there, since I choose not to add MSG to my home cooking. This is the element of flavor many people do not recognize in Japanese cooking. Oh, and that wood shaving thing...when I was a kid, maybe 10 or 11, I was learning to help cook with my mom and grandmother and decided to help by shaving the bonito stick in the new katsuoboshi shaver. I took what I thought was the bonito stick, but was actually my grandmothers surikogi, an old one at that, and proceeded to shave it. It smelled oddly of pepper and wood, not the expected fish. Hmmm...there was lots of yelling, something about 'bakatare'. You try to help...