Make fish Dashi broth. Put 4 cups of water in a pot with dried anchovies. Let soak for 30 minutes, and then cook for 5 minutes. Remove fish. Or you can opt for other Dashi from our Dashi recipes.
Cut Aburaage thin Tofu into 1/2" (1.25 cm) strips. For the white part of the long onions, cut into thick pieces. For the green part, slice very thinly. Set aside the green part of the onions for later.
Add Tofu and the white part of the onions to the Dashi broth, cover, and cook for a couple of minutes.
Dissolve Miso Paste in the Dashi broth. Add the green part of the onions. Serve immediately.