Ingredients

2 tablespoons extra-virgin olive oil

1 tablespoon freshly grated ginger

4 scallions, whites and greens separated and thinly sliced

3 cloves garlic, minced

4 ounces shiitake mushrooms, trimmed and thinly sliced

1 sweet potato, peeled and diced

4 ounces soba or other buckwheat noodles

2 heads baby bok choy, sliced in 1/2-inch pieces

1/2 cup sweet white miso

1 tablespoon fresh lime juice, plus lime wedges for serving

Kosher salt

Preparation

In a medium pot, heat oil over medium heat. Add ginger, scallion whites, and garlic and cook until fragrant, about 2 minutes. Add shiitakes and cook until tender, about 2 minutes. Add sweet potato and toss to coat. Add 6 cups water and bring to a boil, then reduce heat and simmer until sweet potatoes are tender, 6 to 8 minutes.

Meanwhile, cook soba according to package instructions. Drain and rinse well with cold water. Set aside.

Add bok choy to soup and cook until tender, about 2 minutes. Stir in cooked soba.

Remove 1 cup hot broth and whisk with miso until smooth, then stir into soup. Add lime juice and season with salt. Serve with scallion greens and lime wedges.