Step 1

Put 3 cups (24 fl. oz./750 ml) cold water and the kombu in a saucepan over medium heat. Bring to a boil and then remove and discard the kombu. Turn off the heat, add the bonito flakes, stir gently once and let sit for 5 minutes. Strain the soup through a fine-mesh sieve and return the broth to the saucepan.

Step 2

Put the miso paste in a small bowl and add 1⁄4 cup (2 fl. oz./60 ml) of the warm broth. Stir until the mixture is very smooth. Add the miso mixture to the saucepan and warm gently, taking care not to let the soup come to a boil.

Step 3

Place a small frying pan over high heat until it is very hot. Rub the cod with the oil and season with salt and pepper. Sear until just cooked through, about 4 minutes per side.

Step 4

To serve, ladle the soup into bowls, top with one or two pieces of fish, and sprinkle with green onions. Serves 2.

Step 5

Adapted from Williams-Sonoma Soup of the Day, by Kate McMillan (Weldon Owen, 2014)