Soak the soybeans in a large bowl and cover with a generous amount of cold water. Let soak for around 12 hours or until the beans have swelled up into an oblong shape rather than round.
Drain the beans in a colander, rinse and pick out any dark or discoloured beans.
Blend beans with 8 cups of water, before straining through a nut bag or cloth-lined colander. You'll need to do this in three to four batches to accommodate the standard blender size.
Blend on high until the mixture forms a slurry. It should be milky and smooth with a fine grain left behind. If you over blend, your milk will be too sludge-like, but if you under blend, the milk will run too thin.
Pour the soy milk slurry through a nut bag or muslin cloth-lined colander. Squeeze the bag to pour out every last drop. The remains are called okara and can be used as the base for many great recipes.
Pour strained soymilk into a large pot over medium-low heat and simmer for a few minutes or until skin begins to form on top. It's essential to watch the pot and stir constantly because it boils over quickly.
The bottom is also at high risk of burning.Bring the heat to a boil and pour one teaspoon of liquid nigari—lower the heat. The milk should begin to curdle. If it doesn't separate, add the remaining half teaspoon of nigari.
Line a tofu press or colander with cheesecloth and slowly pour the tofu mixture over the sink.
While still in the tofu press or colander, wrap the top of the tofu and place a weight over the mixture to press it down. A few cans work well here. The more your press your tofu, the firmer it becomes. If you prefer fresh tofu ricotta, skip this step.