Soak 1 cup dried soybeans in plenty of water for 8 to 12 hours
Drain and rinse the soaked soybeans
Rub the beans between your hands to loosen and remove the skins
Rinse again and discard floating skins
Add the soybeans to a blender with 4 cups fresh water
Blend until smooth
Pour the blended mixture into a pot
Add 4 more cups water to the blender, swirl, and pour into the pot
Bring the mixture to a boil over medium heat
Stir often to prevent sticking and overflowing
Simmer for 15 to 20 minutes
Turn off the heat
Strain the mixture through a nut milk bag, cheesecloth, or fine sieve
Squeeze out as much liquid as possible
Collect the soy milk in a clean container
Sweeten or flavor if desired
Refrigerate and use within 3 to 5 days