Dice the tofu into cubes, and finely chop the green onions. Soak the dried wakame, and squeeze out any excess water.
Heat 320 cc of water in a pan. Add the tofu and wakame.
When the water comes to a boil and the ingredients are cooked, turn off the heat. When the boiling soup has settles, dissolve the miso into the soup. Carefully reheat the soup, being careful not to bring it to a boil. Add the green onions just before the soup begins to boil and turn off the heat.