Soak black soybeans in water for 8 hours.
Boil the soaked beans in boiling water for 20 minutes.
Peel the skin off the boiled beans.
Blend the beans and water until smooth.
Strain the blended mixture through a fine sieve.
Put the strained soybean mixture into a pot and simmer on medium-low heat, stirring until it thickens to a creamy consistency.
Season with salt to taste.
Transfer to a plate to finish.