We just got back from an amazing family trip to Asia, and I'm excited to share a yummy miso soup recipe we learned while staying in Japan. This is as close as you can get to the traditional way they make it over there.
Pour the cold water into a medium pot and add the kombu. Soak for 30 minutes (or more if refrigerated).
Place over low heat and bring to a light simmer (never boil). Turn off heat and remove kombu (discard or use for something else).
Add the bonito flakes to the warm water and wait until they sink, 5 or 6 minutes.
Strain out the bonito flakes by using a fine strainer (or lining a regular strainer or colander with a paper towel), capturing the stock in a pot. Only squeeze very gently to release all the water from the flakes.
To make the Miso Soup
Reheat the dashi (stock). Remove a couple spoonfuls of stock and mix it together with the miso paste in a small bowl.
Add this back to the stock, along with the tofu and green onions. Cook over low heat for a few minutes (do not boil) and serve.