- 5 cups water
- 3/4 ounce kombu (four 5-inch pieces)
- 1/3 cup bonito flakes
- 2 tablespoons soy sauce, plus more for seasoning
- 1 pound kabocha or buttercup squash, peeled and cut into 1-inch pieces
- 3 1/2 ounces White Beech (Bunapi), enoki, or shiitake mushrooms, trimmed
- 8 ounces soba noodles, preferably 100 percent buckwheat
- Silken tofu (optional), for serving
- Thinly sliced scallions, for garnish
- Bring water and kombu to a boil in a large saucepan. Remove from heat, stir in bonito flakes, and let stand 5 minutes. Pour broth through a fine sieve into a bowl, discard solids, and return broth to pan.
- Add soy sauce, squash, and mushrooms to broth. Bring to a boil over high heat, reduce heat, and simmer, stirring occasionally, until squash is tender, about 10 minutes. Season with more soy sauce if desired.
- Bring a large pot of water to a boil. Add noodles, and cook, stirring occasionally, until noodles are al dente, 5 to 7 minutes. Drain, and rinse under cold water.
- Divide noodles among 4 bowls. Ladle soup over noodles, dollop with tofu, and garnish with scallions.
There are no substitutes for kombu and bonito flakes -- two necessary ingredients in the simple Japanese sea stock called dashi -- but they are easy to find at Asian markets, many supermarkets, and asianfoodgrocer.com