Prepare the dashi: put about 4 cups of Water and a small piece of Kombu (wipe, don’t wash) in a pot and let it sit for 20–30 minutes if you have time, or slowly heat until just before boiling. Remove the kombu right before the water reaches a boil so it doesn’t become bitter.
Add the Katsuobushi (bonito flakes) to the hot water, bring to a very gentle simmer for 30 seconds to 1 minute, then remove the pot from the heat and let the flakes steep for 3–5 minutes. Strain the liquid through a fine sieve or cheesecloth into a clean pot to yield a clear dashi.
Rehydrate the Dried Wakame in a small bowl of warm water for 5 minutes until it softens, then drain and gently squeeze out excess water. Set aside.
Cut the Silken Tofu into bite-sized cubes while the dashi is warm. Silken tofu is delicate, so handle it gently to keep the pieces intact.
Warm the strained dashi over low heat, add the softened wakame and tofu, and heat just until warmed through — avoid a rolling boil which can break the tofu and dull the miso flavours.
Dissolve the Shiro Miso by placing it in a small bowl or ladle, adding a few spoonfuls of hot dashi and whisking until smooth. Remove the pot from the heat and stir the dissolved miso back into the soup; do not boil after adding miso to preserve its flavour and beneficial enzymes.
Taste and adjust seasoning if needed, then garnish with thinly sliced Scallions and serve immediately in warmed bowls.
