Rinse the black beans thoroughly and soak them for at least 8 hours.
Boil the soaked black beans in boiling water for 10 minutes.
Blend the boiled black beans with water in a blender until smooth.
Strain the mixture through a sieve to remove the skins.
Pour the soy milk into a pot and simmer for 5 minutes.
Add a pinch of salt or a little honey to taste, and it's ready.