Directions

1. 1

   Divide the fresh spinach among 4 deep soup bowls, setting them aside. Bring a large pot of water to a boil and add a large pinch of salt. Add the soba noodles and stir occasionally to prevent them from sticking together. Cook until the noodles are tender, about 5 minutes. Drain the noodles well and distribute them evenly among the 4 bowls.

2. 2

   While the noodles cook, fill a large saucepan with 8 cups of water and bring it to a boil. Remove from heat and add the instant dashi flakes. Let simmer gently for 7 minutes to allow the dashi flavor to fully develop.

3. 3

   Strain the dashi broth through a fine-mesh sieve into a heatproof bowl, then return it to the same saucepan. Stir in the soy sauce, ginger slices, sliced green onion tops, and a pinch of sugar. Bring the broth to a gentle simmer.

4. 4

   Carefully add the thinly sliced fish (tilapia, salmon, or halibut) to the simmering broth in a single layer, working in batches if necessary. Cook for about 2 minutes, just until the fish becomes opaque and tender but before it begins to flake apart. The internal temperature should reach 145°F. Using a slotted spoon or skimmer, gently transfer the cooked fish slices to the soup bowls.

5. 5

   Bring the remaining broth almost to a boil. Place the white miso in a small heatproof bowl and ladle about 1/2 cup of the hot broth over it. Whisk the mixture vigorously until the miso is completely dissolved and smooth. Pour the dissolved miso back into the saucepan and stir gently to blend it throughout. Simmer very gently—do not allow the soup to boil, as this can diminish the delicate miso flavor.

6. 6

   Ladle the hot miso broth into each of the 4 bowls over the noodles and fish. Garnish with red pepper flakes if desired. Serve immediately while steaming hot.