Ingredients
6 cups water
4 ounces fresh shiitake mushrooms, stems trimmed and reserved, caps cut into 3/4-inch slices
1/2 ounce dried shiitake mushrooms (5 large)
1 six-inch square dried kombu
3/4 cup bonito flakes (1/4 ounce)
1/4 cup plus 1 teaspoon reduced-sodium soy sauce
2 tablespoons mirin
1/2 large sweet potato (about 4 ounces), peeled, halved lengthwise, and cut crosswise into 1/4-inch-thick slices
6 ounces soba noodles (2 bundles)
3 ounces snow peas, trimmed and halved
3 ounces kohlrabi, peeled and cut into 1/4-inch-thick sticks
8 ounces silken tofu, cut into 8 slices
Preparation
Bring 6 cups water, mushroom stems, dried mushrooms, and kombu to a boil in a large pot over medium-high heat. Remove from heat, and add bonito flakes. Let stand until flakes sink to bottom of pot, about 3 minutes.
Line a sieve with cheesecloth. Strain broth through sieve into pot, and discard solids. Stir in soy sauce and mirin. (You should have 5 cups.)
Cook sweet potato in a large pot of boiling water until crisp-tender, about 2 minutes. Transfer to a bowl using a slotted spoon. Add noodles to boiling water. Cook according to package directions. Drain. Rinse with cold water.
Divide noodles among 4 bowls. Arrange sweet potato, sliced mushroom caps, snow peas, kohlrabi, and tofu on top of noodles. Bring broth to a simmer, then immediately divide among bowls. Serve immediately.
