This is a long-promised recipe for Becky. It's hard to make it into a recipe, because I just sort of wing it now.
This involves some very specific Asian ingredients, so get yourself to your local Asian market.
6-9 c. dashi (I use instant dashi, you can make your own using bonito flakes and water)
miso paste (I like the yellow or white miso, because I think it's milder. You can use red if you like)
rehydrated Wakame seaweed (just steep it in warm water for a few minutes)
extra-firm tofu, drained and cubed
Get the dashi almost boiling in a pot, then begin to slowly whisk in miso. I start with 2 Tbsp., then taste and add more as needed. I don't like my soup quite as salty as most sushi restaurants make it, but the beauty of making your own is you can make it as salty as you like.
Once you've got the stock and miso combined, add the Wakame and tofu, and heat through.
Sometimes I add mushrooms, noodles, bean sprouts or shrimp to the soup. Mostly we eat it with just tofu and seaweed.