Yasai-To-Tofu-no-Misoshiru (Hearty Miso Soup with Vegetables & Tofu)

1. To prepare dashi: Heat water and kombu in a large pot over medium heat until bubbles begin to form around the kombu, 5 to 10 minutes. Remove the kombu, continue cooking until the water comes to a boil, then remove from heat. Add bonito flakes and let stand for 2 minutes. Strain the dashi through a fine-mesh sieve into a large glass measuring cup or heatproof bowl. (Do not press the bonito flakes while straining as it will cloud the dashi.) You should have 5 cups.

2. To prepare miso soup: Heat oil in a large saucepan over medium heat. Add onion and cook, stirring occasionally, until soft, about 5 minutes. Add carrots, sweet potato, daikon and shiitakes. Cook, stirring occasionally, until the vegetables start to soften, about 5 minutes. Add 4 3/4 cups of the dashi and bring to a boil over medium-high heat. Reduce heat to maintain a simmer and cook until the vegetables are soft, about 6 minutes.

3. Pour the remaining 1/4 cup dashi into a small bowl and whisk in miso. Add the miso mixture and tofu to the soup and stir. Serve the miso soup topped with scallions and lemon zest and garnished with shichimi, if desired.

To make ahead:

Refrigerate the dashi (Step 1) for up to 3 days.