In a large bowl, mix flour and salt.

Gradually add water to the flour mixture, stirring until a dough forms.

Knead the dough on a floured surface for about 10 minutes until smooth.

Wrap the dough in plastic wrap and let it rest for 30 minutes.

Roll out the dough to about 1/4 inch thickness.

Cut the rolled dough into 1/4 inch wide strips for udon noodles.

Dust the noodles with cornstarch to prevent sticking.

Boil water in a large pot and cook the noodles for 8-10 minutes until tender.

Drain the noodles and rinse under cold water.

In a pan, heat sesame oil and sauté mushrooms and bok choy until tender, then add the udon noodles and soy sauce.