In a medium saucepan, combine 4 cups of cold, filtered water with a piece of dried kombu. Let the kombu soak for 10 minutes. Heat until just about to boil, then remove the kombu.

Bring the water to a gentle simmer. Add 1 cup of bonito flakes and let it simmer for about 60 seconds. Turn off the heat, letting it sit for 3 minutes. Strain the broth into a bowl.

While the dashi is resting, rehydrate 1 tablespoon of dried wakame seaweed in a bowl with cold water for 5 minutes. Drain and squeeze out excess moisture.

Return the strained dashi broth to the saucepan. Mix 3 tablespoons of awase miso paste with a few spoonfuls of hot dashi to create a slurry. Gradually stir it into the broth.

Add cubed soft silken tofu and the rehydrated wakame to the broth. Warm the soup for an additional 1-2 minutes without boiling. Ladle into bowls and garnish with fresh scallions.