Add the 4 cups water and 1 piece kombu about a 4-inch square piece to a saucepan. Let the 1 piece kombu about a 4-inch square piece soak for at least 5 minutes (or up to 30 minutes if you have time) — this cold-steeping draws out its natural glutamates for a deeper broth.

Place the saucepan over medium heat. Warm the 1 piece kombu about a 4-inch square piece in the 4 cups water until it just begins to simmer — small bubbles will appear around the edges. Remove and discard the 1 piece kombu about a 4-inch square piece just before the 4 cups water reaches a full boil.

Add the ½ cup katsuobushi (bonito flakes) loosely to the hot 1 piece kombu about a 4-inch square piece 4 cups water. Bring to a gentle simmer over medium heat, then immediately turn off the heat. Let the flakes steep undisturbed for 3 minutes — do not stir.

Strain the broth through a sieve into a clean mixing bowl or pot, pressing gently on the ½ cup katsuobushi (bonito flakes) loosely to extract all the liquid. Discard the solids. Your dashi is ready.

Return the dashi to the saucepan over medium-low heat. Add the 7 oz silken or soft tofu cut into small ½-inch cubes cubes and rehydrated 2 tbsp dried wakame seaweed rehydrated in cold water for 5 minutes,. Warm gently until the broth is steaming hot but not boiling — about 2 minutes.

Place the 3 tbsp white miso paste in a small ladle or a separate mixing bowl. Scoop out a few tablespoons of the hot dashi and whisk it with the 3 tbsp white miso paste until fully dissolved and smooth. Stir this 3 tbsp white miso paste mixture back into the pot.

Taste the soup. It should be savory, lightly salty, and balanced. Add a little more dissolved 3 tbsp white miso paste if you prefer a stronger flavor. Keep the heat on the lowest setting — the soup should be steaming but never boiling.

Ladle the soup into bowls and top with sliced stalks green onions (scallions) thinly sliced. Serve immediately.