In a large bowl, mix the buckwheat flour and all purpose flour
Add one egg, mix it into the flour using a folk
Gradually sprinkle 1/4 cup water into the flour, while mixing using the folk. This will generate coarse crumbs, instead of a soft dough.
Further mix the crumbs by hand to help distribute liquid more uniformly in the flour. Gather them into a dough and knead for 3 minutes. The dough should be firm without being sticky. It has rough surface like a piece of rock.
Seal the dough into a ziploc bag. Let it rest for 30 minutes at room temperature.
Take the dough out. It feels softer after resting. Knead for 5 minutes. The dough becomes smooth and more elastic.
Seal the dough into the ziploc bag and let it rest for 30 minutes at room temperature.
Put the dough on a cutting board, and press it down into a round disk using your palm. Dust the board and both sides of the dough with corn starch.
Using the rolling pin, roll out the dough from the center outwards in all directions.
Once the dough is rolled into a sheet with 1/2 inch thickness, cut the sheet into 4 portions. Dust with more corn starch as needed.
Roll out each sheet into the preferred thickness. Fold and overlay them on top of each other. The vertical width of the sheets should be less than the length of your kitchen knift. Dust between layers with corn starch as needed to prevent them from sticking to each other.
Cut the sheets into 1/8 inch-wide noodles.
To cook the noodles, bring water to boil in a large pot. Add 1 teaspoon of salt and 1 tablespoon of cooking oil to the water. Add noodles into the boiling water and cook at medium high heat for 3 minutes. Drain the noodles and mix in 1 tablespoon of cooking oil. Add sauce and sprinkle with fresh herbs.