Obviously, you can’t make miso soup without miso. However, the dashi is absolutely essential; miso soup = dashi + miso + stuff.
Dashi is usually referred to as a broth, but infusion would be a better term. The most standard form of dashi is made from kombu seaweed and bonito flakes but many variations exist. You can make a vegan dashi, but meat, on the other hand, is never used for dashi.
Here are a couple of dashi recipes:
Bonito dashi
2 cups water
A 10cm strip of dried kombu seaweed.
A fistful of bonito flakes (about 20g)
Rub lightly the seaweed with a moist cloth to remove any dirt or extra sea salt. Place the kombu in the water, which should be cool or at room temperature. Bring to a boil, but remove the kombu just before the water actually boils. When the water is boiling scoop up any foam that might form. Remove from heat. Add bonito and let infuse until the flakes sink to the bottom. I usually infuse for about 3 minutes. Strain and you’re done.
Vegan dashi
2 cups of water
A 10cm strip of dried kombu seaweed.
Dried shiitake mushrooms (about 20g)
Proceed as with the bonito dashi but stop when you’ve removed the kombu. Let the dashi cool back to room temperature. Clean the mushrooms of any dirt and put in the water. Wait a few hours until the mushrooms are soft. Remove the mushrooms and you’re done. You can add the mushrooms back to your soup later but make sure you cut off the stems.
The last recipe takes a bit of time. You might ditch the kombu, as the shiitake will provide the necessary umami. You can also make dashi from other types of dry fish but I think they might be hard to come by outside of japan. I also once did the shiitake dashi and added some dry morrells. Very awesome.
Once you have your dashi, you can then add things to your soup. I added a list at the end of the post, but since people have miso soup almost everyday here, you’re going to find a huge range of variation. Add in the miso at the very end and whatever you do, do not boil it.
Things that might go in a miso soup:
Tofu (both “silk” and “cotton”, but not the hard crap they sell in North American health food stores)
Various kinds of mushrooms, but, more authentically, shiitake or enoki.
Japanese radish (daikon)
Asparagus
Potatoes
Okra
Squash/Pumpkin
Malukhiyah
Spinach
Cabbage
Chinese cabbage
Onions
Bamboo shoots
Burdock
Eggplant
Lotus root
Etc…