In a large mixing bowl, dissolve 1 teaspoon of salt in the 180ml of water. Gradually add the salted water to 400g of flour. Begin mixing the dough with your hands or a wooden spoon, combining until it forms a rough dough.

Once the dough starts to come together, transfer it to a clean surface and knead for about 10 minutes. The dough should become smooth, firm, and elastic. If the dough feels too sticky, sprinkle a bit more flour, but avoid over flouring to maintain the right texture.

After kneading, shape the dough into a ball and wrap it tightly in plastic wrap. Let the dough rest for at least 30 minutes at room temperature. This resting time helps relax the gluten and makes it easier to roll out.

Once rested, dust a clean surface with cornstarch or potato starch. Unwrap the dough and roll it out into a flat rectangle about 0.5 cm thick. Make sure to dust the dough and rolling pin lightly with starch to prevent sticking.

To cut the udon noodles, fold the rolled dough into thirds (like folding a letter) and slice it into even strips about 0.5 cm wide. Carefully unfold the strips and dust them with starch to prevent sticking.

Bring a large pot of water to a boil. Gently shake off excess starch from the noodles and add them to the boiling water. Cook for about 8-10 minutes or until the noodles are tender but still have a slight chew.

Drain the noodles and rinse them under cold water to remove any excess starch and to stop the cooking process. Set the noodles aside while you prepare the broth or toppings.

Serve the udon noodles in a hot dashi-based broth or with your choice of toppings like tempura, scallions, and a soft-boiled egg. You can also serve the noodles cold with dipping sauces. Garnish with finely sliced green onions or nori for added flavour.