If you grind one cup of black soybeans for about 30 minutes while heating, it becomes soy milk.
Wash the black soybeans thoroughly and soak them for at least 6 hours.
Boil the soaked black soybeans in boiling water for 10 minutes.
Drain the boiled black soybeans.
Add the black soybeans, water, and salt to a blender and blend until smooth.
Strain the mixture once through a fine sieve.
Pour the strained soy milk into a pot and simmer over low heat for 10 minutes, stirring continuously.
Pour the finished black soybean soy milk into a cup.