Soak the soybeans in water for at least 8 hours.
Boil the soaked soybeans in boiling water for 5 minutes.
Rinse the cooked soybeans in cold water and peel off the skins.
Place the peeled soybeans and cold water in a blender and blend until smooth.
Strain the blended soybean mixture through a sieve to make a smooth soy milk soup base.
Season the soybean soup with salt or sugar to taste.
Rinse the cooked somyeon noodles in cold water and drain well.
Place the somyeon noodles in a bowl and pour the soy milk soup over them.
Garnish with cucumber, tomato, or other toppings to finish.