Japanese
Soak the dried wakame in cold water for about 5 minutes until it rehydrates and expands, then drain.
Heat the dashi in a saucepan over medium heat until steaming but not boiling.
Add the tofu cubes and wakame and warm through gently.
Place the miso paste in a ladle or small bowl, add a little of the hot dashi, and whisk until smooth.
Stir the dissolved miso back into the pot and keep the soup just below a simmer, never letting it boil.
Divide between bowls, scatter with spring onion, and serve immediately.