Wash soybeans thoroughly and soak for at least 8 hours.
Peel the soaked soybeans.
Put the peeled soybeans in a blender and blend finely with water.
Pour the blended soybeans into a fine cloth and squeeze.
Put the squeezed soybean liquid in a pot and cook over medium heat, stirring.
When it starts boiling, reduce to low heat and simmer for 5 more minutes. Done.