Yudofu is one of the dishes made with tofu. It's a typical winter hot-pot dish.
Place kelp in the bottom of a pot, put bite-sized tofu into the water in the pot, and eat it with dipping sauce, removing it from the water once it's sufficiently warm. It is supposed to be good to eat tofu when it sways, but without over-boiling it.
In any case, tofu, water and kelp are the only ingredients, but they all must be of good quality. Particularly, good water is an absolute necessity, and therefore the ones from Kyoto are renowned.
The dipping sauce (a kind of soy sauce) uses a mixture of soy sauce, sake, mirin and stock, or Ponzu soy sauce; for the condiments, green onion, yuzu, grated daikon (grated ｄaikon and red pepper) or dried bonito shavings are often used.
It is said that adding a pinch of salt or chopped Daikon makes tofu soft without being pithy. Chinese cabbage or slices of cod can also be boiled together with tofu. However, it is said that overly strong ingredients will spoil the traditional, light flavor of this dish.
This is mainly for winter, but some people have it as a summer hot-pot dish.
A character in a novel by Shotaro IKENAMI ate one on a cold day during the rainy season; also, IKENAMI wrote a short story called 'Yudofu in the Rainy Season.'
IKENAMI was a gourmet, and he used broiled and sun-dried Ayu as stock, which was extravagant.
For 'Yu-yakko' described as 'superb' in 'A Hundred Delicacies of Tofu,' a cookbook dating from the Edo period, kudzuyu is used instead of water, which maintains the warmth of tofu until it is eaten and gives one the chance to enjoy the pairing of tofu and Kudzuyu.
There is a famous Japanese poem about Yudofu by Mantaro KUBOTA: 'In eating simmering tofu, one realizes that life is nothing but twilight in the end.'