Pour the dashi water into a large pan and add the wakame. Then bring to a boil. The wakame will increase in volume so it is very important to choose a large pan.
In a bowl, mix the miso paste with some of the soup until it is completely dissolved.
Reduce the heat so that the soup stops boiling. Add the dissolved miso paste and wakame powder to the soup.
Then add the cubes of tofu to the soup and add the Shichimi togarashi herbs to taste.
Divide the soup into serving bowls and finish with the chopped spring onions.