Hot Soba Noodle Soup With Salmon, Cucumber, And Togarashi

To make noodle broth (kakejiru): Add the dashi, salt, soy sauce, sugar, mirin, plus 1/2 cup cold water to a pot over medium-high heat and bring to a boil. Remove from heat.

To make soba: Boil noodles according to package directions. Drain in fine-mesh strainer and rinse well under cold water. Shake them dry.

To serve: Divide noodles among four bowls. Add broth. Top each bowl with vegetables, salmon, shichimi togarashi, and bonito flakes.

To pack for lunch: Divide vegetables, salmon, and noodles between four large mason jars or containers. Starting with the scallions, then watercress, cucumber, daikon, and salmon, stack them in the jar or container. Add the cooked soba noodles last. Twist a lid on securely, turn upside down and store in refrigerator, so that the toppings sit on top. Divide the noodle broth between four more containers, so the broth and noodles are packed separately. When you're ready to eat, gently reheat the noodle broth. Carefully open the upside-down mason jar or container into a bowl so that the noodles fall in first and the rest of the ingredients sit on top. Pour broth into the bowl. Garnish with shichimi togarashi and bonito flakes.

Rinse konbu under cold water and place it in a medium pot with 2 quarts cold water. Heat over medium-high heat until tiny bubbles form at the edges, about 12-14 minutes. Don't let the water come to a full boil, which will bring out bitter flavors. If you can puncture the kombu easily, it is ready; remove it with tongs. If it is still stiff, leave it in the pot, add about 1/4 cup more water and cook for another few minutes.

After removing the konbu, add 1/2 cup cold water and bonito flakes. Bring just to a boil, about 2 minutes, and then remove from the heat and cover. Don't let the dashi boil too long or the bonito flavor will be quite strong. Let it sit until the bonito flakes settle at the bottom of the pot, about 10 minutes. Strain through a fine-mesh sieve or cheesecloth into another pot. Do not press the bonito flakes. The used konbu and bonito flakes can be refrigerated or frozen and used one more time to make a second dashi. The dashi will keep in the refrigerator for a few days and in the freezer indefinitely.