Combine flour, buckwheat flour, and salt in a medium-sized bowl.
Add olive oil, egg, and water to flour mixture.
Stir until a shaggy dough forms.
Turn dough out onto a clean work surface and knead until smooth and uniform, about 5 minutes.
Wrap in plastic and let rest for 30 minutes.
Divide dough into four pieces and roll and cut into thin strands like spaghetti, transferring to a towel-covered drying rack as you work. Let noodles dry part way.
Bring a large kettle of salted water to a boil, add noodles, and boil, stirring and adjusting heat as necessary, until noodles are tender, about 3-5 minutes.