Arrange the leeks, chili powder, ginger, and nori on a platter and place on the table. Set a charcoal brazier or gas burner at the center of the dining table. Atop heat source place a large casserole, tureen, chafing dish, or copper pot.
Place kombu at the bottom of casserole and set the cup of dipping sauce top the kombu.
Now fill the casserole with boiling water, return to the boil and drop in tofu. Invite each guest to ladle some of the dipping sauce into a small dish provided for this purpose and add to it his choice of garnishes and seasonings. After 2 or 3 minutes, or as soon as the tofu begins to sway in the simmering water or float to the surface, each guest uses a slotted spoon or pair to chopsticks to lift out the tofu. Dip tofu into sauce and garnish mixture before eating.