Step 1Place the water in a saucepan and bring it to a boil. Turn off the heat and let cool for 1 minute. Add the bonito flakes and allow the flakes to steep in the liquid about 5 minutes.
Step 2Strain the stock through a fine strainer, but do not press down on the bonito flakes or the stock will be cloudy. Makes about 3 1/2 cups.
Step 1Bring the broth, soy sauce, mirin and sugar to a boil in a medium saucepan. As soon as it comes to a boil, turn off the heat and add the bonito flakes.
Step 2Allow the mixture to steep for about 1 minute before straining the dipping sauce through a fine strainer. Do not press down on the bonito flakes or the sauce will be cloudy. Makes about 3 cups.
Step 3Bring a large pot of lightly salted water to boil over high heat. Add the soba noodles and cook until foam rises to the top, about 30 seconds. Reduce heat and simmer until the noodles are tender but springy. Depending on the brand, this can take anywhere from 1 to 5 minutes; the only way to be sure is to taste.
Step 4When the noodles are done, drain them and rinse under cold running water until the water runs clear. When the noodles are cool, drain them again and divide them among 4 bowls. Serve the room temperature noodles with a small bowl (about two-thirds cup) of dipping sauce on the side. Any leftover dipping sauce can be kept tightly covered and refrigerated for up to a week.