Kombu Chicken Soup with Carrots and Mushrooms

 

10 ounces mature spinach (about 1 bunch), trimmed

3 6×4-inch pieces dried kombu

6 cups homemade or store-bought low-sodium chicken bone broth

1 cup bonito flakes

2 T. mirin

2 T. soy sauce

Kosher salt

2 boneless, skinless chicken breasts, halved lengthwise, thinly sliced crosswise

1 medium carrot, peeled, cut into 2-inch matchsticks

4 ounces shiitake mushrooms, stemmed, thinly sliced

Toasted sesame seeds (for serving)

 

Heat ¼ cup water in a large skillet over medium. Once you see steam, add spinach to water and cook, tossing often, until spinach begins to wilt, about 2 minutes (work in batches if necessary). Transfer to a colander and let cool. Squeeze spinach to remove excess water, then coarsely chop; set aside. Bring kombu and stock to a simmer in a large saucepan over low heat. Remove from heat and let sit 10 minutes. Return to a simmer and add bonito flakes. Remove from heat and let sit 2 minutes. Strain kombu mixture through a fine-mesh sieve into a large bowl. Wipe out saucepan and return broth to saucepan. Add mirin and soy sauce; season with salt. Bring to a simmer over medium heat, then add chicken, carrots, and mushrooms. Cook until chicken is cooked through and mushrooms and carrots are just tender, 4–6 minutes. Divide spinach among bowls and ladle in soup. Sprinkle sesame seeds over.