Miso-Squash Soup With Sesame-Ginger Apples

Ingredients

1 1/2 quarts plus 2 cups water, divided, plus more as needed
1/2 ounce kombu (approximately a 4- by 6-inch piece; see notes)
1/2 ounce grated bonito flakes (about 3 cups; see notes)
1 tablespoon plus 1 teaspoon vegetable oil, divided
1 leek, white and light green parts only, diced (about 1 1/2 cups)
2 medium carrots, diced (about 1 cup)
2 medium cloves garlic, sliced
2 (1 1/2-inch) knobs ginger, 1 knob peeled and thinly sliced, 1 knob peeled and finely grated, divided
1 (2-pound) squash, such as kuri, kabocha, or butternut, peeled, seeded, and diced
2 tablespoons white or red miso paste
1 tablespoon fresh juice from 1 lemon
1 teaspoon kosher salt, plus more as needed
Pinch sugar, if needed
1 large crisp apple, such as Fuji, peeled, cored, and diced
1 large or 2 medium scallions, white and light green parts only, thinly sliced on the bias
1 teaspoon toasted sesame seeds
1/2 teaspoon toasted sesame oil
1 teaspoon rice vinegar

Combine 1 1/2 quarts water, kombu, and bonito flakes in a large saucepan and bring to a boil over high heat. Reduce to a bare simmer and cook for 5 minutes. Remove from heat, let cool for 5 minutes, then strain through a fine-mesh strainer. Discard solids and set dashi aside.
In a large Dutch oven or soup pot, heat 1 tablespoon oil over medium-high heat until shimmering. Add leek, carrot, garlic, and sliced ginger. Cook, stirring, until vegetables are glistening and just starting to turn tender, about 4 minutes.
Add squash and pour just enough dashi on top to cover vegetables. Bring to a simmer and cook until vegetables are fully tender, about 30 minutes. Using a standing blender or immersion blender, and working in batches if necessary, blend soup until very smooth. Blend in miso and lemon juice.
Return soup to pot and thin with enough water to reach a pourable, silky-smooth consistency. Season with salt, add sugar to taste, and keep warm.
Meanwhile, fill a medium bowl with 2 cups water and 1 teaspoon kosher salt. Add diced apple and let soak for 10 minutes. Drain apple well, then return to bowl. Toss with grated ginger, scallions, toasted sesame seeds, sesame oil, rice vinegar, and remaining 1 teaspoon vegetable oil. Season with salt, if needed.
To serve, ladle hot soup into bowls and top with the apple-scallion salad.