Place the dashi or mushroom broth in a large stockpot. Add 1 quart of water, cover, and bring to a boil.
While the broth is coming to a boil, dry the tofu with paper towels and dice. Then cut the nori sheets into small ¼-inch pieces with kitchen shears. Chop the green onions.
Once the broth reaches a boil, turn off the heat and whisk in the miso paste. Once dissolved, add the tofu, nori, and green onions. Stir and serve.
