Pour filtered water on dried kelp. Cover and infuse for a minimum of 30 minutes up to 2 hours.
Note: in order to extract seaweed properties make sure the water is cool or at room temperature.
Chop the shiitake (or rehydrate the dry ones in boiling water for 15-20 minutes), and sauté with a touch of sesame oil and a pinch of salt in a wok for 3-4 minutes (alternatively, for an oil-free version you can add them to the dashi in the next step).
Add the dashi to the wok, set the heat to low and slowly warm the broth until it starts to bubble.
Remove kelp seaweed as soon as it forms little bubbles as shown in the picture. We don't want to cook the kelp in order to keep all its properties. For the oil-free version add the shiitake now, cover with a lid and cook on low heat for 20 minutes.
Cut the silken tofu into cubes and finely slice the green part of the spring onions and add to the broth.
Boil for 2-3 minutes, just enough time for the tofu to warm. Then turn off the heat and dissolve the miso paste into the broth. Please note: we don't want to actually cook the miso paste; it should be added at the very end before serving.
Give the soup a little stir and serve it straight away.
*the nutrition facts are for 1 portion served as a main.