I highly recommend getting kombu, which is a kind of seaweed that allows you to create your own dashi stock. It adds tremendous depth of flavor and all the umami in the world. All you need to do is pour two cups of water into a bowl or pot, put a piece of kombu into it, and let it sit like that for as long as you can. No heat necessary. When you’re ready to start cooking, remove the kombu from the liquid and discard. Use the liquid as your dashi stock. I usually start the soaking process in the morning, but even a couple hours ahead is good too. If you don’t have kombu, you can sub two cups chicken stock for the dashi stock.