This recipe was adapted from Harumi's Japanese Home Cooking, by Harumi Kurihara.

Steps

1. Combine the flours and salt in a large bowl. Add the water and stir until the dough begins to come together. It will be dry and shaggy. Begin kneading by hand in the bowl. If there are still dry sections that refuse to combine, add water as necessary, 1 teaspoon at a time. Turn the dough out onto a floured surface and knead 5 to 10 minutes.
2. Place the dough in a heavy-duty, 1-gallon, zip-lock bag, and seal the bag. Place the bag on the floor, cover with a towel, and stomp the dough flat until it fills the bag. Remove the dough to the floured surface, roll it out with a rolling pin, fold it up, and return it to the bag. Stomp on it again. Repeat the rolling, folding, and stomping routine twice more, for a total of four stomping sessions. Leave the dough in the bag at room temperature 3 to 4 hours.
3. Remove the dough from the bag, form it into a ball, and return it to the bag. Stomp it flat one last time, trying to get it as flat as possible. Remove the dough from the bag and roll it out on the floured surface to ⅛-inch thick. The dough will fight back; if necessary, let it rest 10 minutes and roll again.
4. Fold the dough up in thirds (like you’re folding a letter to put into an envelope) and cut into ⅛-inch-wide noodles with a sharp knife. Toss the noodles with flour and cook promptly to avoid sticking.
5. Bring a large pot of water to a boil. Add the noodles (you’ll probably need to cook them in two batches) and boil 5 to 7 minutes. They’ll cook up very chewy; this is part of their charm.
6. Drain the noodles, rinse with cold water, and toss with peanut oil. If not using the noodles right away, refrigerate them for up to two days. Reheat by boiling for 1 minute.