Time: 45 minutes.

Salt

3 cups lightly packed shaved bonito flakes

3/4 cup soy sauce, preferably light (not low-sodium but usukuchi)

1/4 cup mirin

2 tablespoons sugar

1 sheet nori

4 eggs

About 1 pound soba noodles

1/2 cup chopped scallions.

1. Heat the oven (or a toaster oven) to 300. Bring a large pot of salted water to a boil. In another large pot, bring 10 cups of water to a boil; stir in the bonito flakes, turn off the heat and steep for 10 minutes, no more. Strain into a large bowl; discard the flakes.

2. Put the soy sauce, mirin, sugar and a pinch of salt in the pot you used to make the broth; bring to a boil. Let it boil for a minute, then add the bonito stock; bring it back to a boil, and transfer 6 cups to a separate pot and keep hot. (This will be the broth for the soup; what remains is for cooking the eggs.) Toast the nori in the oven until slightly crisp, about 5 minutes. Cut into quarters and set aside. Crack the eggs into a bowl or a large measuring cup with a spout and beat until frothy.