Step 1In a medium size pan, bring the water, bonito flakes, softened shiitake mushrooms, mirin and light color soy sauce to a boil over high heat. Reduce the heat and simmer gently for 3 minutes to infuse the flavors. Remove from heat, strain the sauce and discard the bonito flakes. Reserve the shiitake mushrooms; remove any tough stems and slice them thinly and use them as a condiment for the noodles. Let the dipping sauce come to room temperature, then refrigerate, covered until needed. This makes 3 1/2 cups sauce and will keep for 1 week, refrigerated.
Step 1In a medium, nonstick frying pan, heat a few tablespoons of the sesame oil and fry the eggplant until it is lightly browned on both sides and cooked through, about 5 minutes. Remove from heat and place on a serving dish.
Step 2Arrange the remaining condiments except the nori (myoga, shiso, scallions, plum paste, ginger, toasted sesame seeds, shichimi pepper, sansho pepper, wasabi paste and sliced shiitakes) on the same serving dish or in separate serving dishes.
Step 3Cook the somen: Bring a large pot of water to a boil and add the noodles, spreading them apart so they do not stick together while cooking. When the water returns to a boil, add half-cup tap water. Cook the noodles so they are al dente, about 3 minutes total cooking time. Immediately remove from heat.
Step 4Drain the noodles and cool them in a large bowl of water under running tap water. Gently swirl the noodles in the running water until the water runs clear. Drain the noodles again.
Step 5Place the noodles in a glass or pottery serving bowl. Add the ice and enough water to mostly cover the noodles. Chill for at least 3 to 5 minutes before serving.
Step 6Bring the chilled noodles to the table, along with the condiments. Arrange the nori with the rest of the condiments or in its own serving dish (arrange the nori last as it will wilt quickly around any sort of moisture). Pour one-third cup (or more as desired) dipping sauce into individual serving bowls for each of the guests.
Step 7Allow the guests to serve themselves, first by taking some of the noodles, then garnishing with condiments of their choice. Make sure guests garnish with the nori last so it stays dry until it reaches the mouth. When guests finish the first batch, go for seconds and thirds.