A few notes to start with.
Since the water is not allowed to reach boiling point, if you have sanitation problems with your tap water, I suggest you used filtered bottled water.
I always thought that silken tofu was used for making miso soup. And I did use silken tofu with my first attempts. Then, I discovered Japanese tofu. The texture and flavor are different.
8 cups of water1
1 packet of powdered dashi
1 cake of Japanese tofu2
2 heaping tsps. of miso paste
patis (fish sauce), to taste
dried wakame, torn and soaked until soft
sliced onion leaves for garnish
Dissolve the dashi in the water and heat without allowing to reach boiling point.
Cut the tofu into half-inch cubes and add to the broth. I suggest leaving the tofu there, over low heat, to allow it to absorb the flavors of the dashi.
Take a few tablespoonfuls of the broth, add to the miso paste and stir until well-blended. Pour into the dashi broth and stir. Add the the wakame. Season with patis.
Ladle into soup bowls, garnish with onion leaves and serve at once.