Soak black soybeans overnight.
Boil the soaked soybeans in boiling water for 10 minutes.
Rinse in cold water, then grind finely in a blender with water.
Season with salt.
Cook the noodles and rinse in cold water.
Place cooked noodles in a bowl and pour the soybean soup over them.
Top with sliced cucumber and sesame seeds to taste.