Whisk together water and salt then add in egg yolk.
Put flour into a medium bowl and make a well in the center; pour in egg mixture.
Use a fork to combine mixture into a crumbly dough.
Pour out onto a well floured surface. Knead dough by hand until smooth and slightly elastic.
Cover in plastic wrap and rest for 20 minutes.
Preheat oven to 300 degrees.
Cut dough into four pieces. Roll until you think they are thin enough, then roll again. Fold dough into thirds, then cut into 1/2-inch wide strips. Unfold and lay on baking sheet. Place in oven for 10-15 minutes until noodles feel mostly dry.
They are now ready to add to soup (or be boiled in water for another use).