How to Make It
In a large bowl, cover the soy beans with 3 inches of cold water. Cover and let stand overnight at room temperature. Drain the soy beans and transfer them to a blender. Add 3 cups of the filtered water and puree at high speed until as smooth as possible.
Line a large sieve with a clean cotton napkin or 3 layers of cheesecloth and set the sieve over a heatproof bowl. In a large pot, bring 3 cups of the filtered water to a boil. Add the soy bean puree and bring just to a boil (be careful not to let it boil over). Boil over moderately high heat for exactly 8 minutes, stirring constantly with a heatproof rubber spatula to prevent sticking and scorching.
Carefully pour the mixture into the prepared sieve. Let stand until just cool enough to handle, about 20 minutes. Gather the ends of the napkin or cheesecloth and squeeze to extract as much of the soy milk as possible; the remaining solids should be nearly dry. Discard the solids and skim off any foam from the soy milk. You should have about 4 cups of soy milk.
In a large, clean saucepan, bring the soy milk to just below a simmer. A skin will slowly form on the surface of the soy milk. When the skin is fully formed, use a paring knife to carefully detach it from the side of the saucepan. Carefully slide a chopstick or skewer under the skin and lift it from the milk. Let drain for a few seconds before transferring to a plate. Repeat, stacking the tofu skins, until the soy milk is depleted.
Dashi, scallions and cilantro.