Looking into the history of "Shiraae," "Shirasu" and "Shiraae" appear in "Ryori Monogatari" (Cooking Story) (published in 1643) from the Edo period. "Put tofu in mustard, add salt, and dilute with vinegar. For Shiraae, do not add vinegar, but grind well." As such, tofu is not the main ingredient like it is today. Mustard is the main ingredient, tofu is added, and the flavor is adjusted with salt. "Shirasu" is when vinegar is added, and "Shiraae" is when it is not. However, according to "Ryori Chinmi-shu" (Collection of Cuisine Chinmi) (published in 1764), which also collected newly made delicacies from "Ryori Sankaikyo" from the Edo period, "Fuji-Shiraae" is listed as the white part of green onion boiled and mixed with tofu with sesame miso, and "Shirae" is listed as diced fish, boiled, mixed with miso, tofu, and sesame. The main ingredient is tofu, just like today. Also, the "white vinegar" mentioned in the Meiji-period "Nihon Ryoriho Taizen" (published in 1898) is mainly made from tofu, as described in the following description: "Drain off the tofu water, add white sesame seeds, grind, mix with vinegar, and strain." Since shojin ryori originally included dishes that used tofu, it seems that "Shiraae," a dish dressed in a white batter, was also heavily influenced by shojin ryori.
It is important to drain the water from tofu when Shiraae. It tastes better if you drain the water while it is still raw, but in seasons when the tofu spoils quickly, it is better to boil it and drain the water. When squeezing the tofu into the cloth, the tofu will ooze out through the grain of the cloth, but be careful not to squeeze too much and let the soy milk come out as well. It is not good to squeeze too much and turn it into a crumbly mess, but not to squeeze too little, so the key is to get the balance right.
Also, make sure to season the ingredients you are going to mix first. In this example, we are seasoning the wild vegetables with a light dashi stock.