They are baked over coals, and sold cooked and hot from wooden carts called “yaki-imo-ya” in the fall and winter, and at fairs. The carts go through neighbourhoods, ringing a bell.
The “carts” are trucks or vans, now used instead of the wooden carts that preceded them. The trucks have small chimneys on them. They also have loudspeakers on them, with recordings that call out very loudly “yaaaaaaakiii — imoooooo” while moving slowly along the street. A very few sellers will still call out live, from a microphone around their necks.
To a Westerner, the first time they hear the chant, it might sound something like a funeral dirge, as it’s actually quite haunting.
The phrases also used in the chant include Fried Sweet Potatoes, Delicious Fried Sweet Potatoes and Sweet Potatoes Fried on Stones.
You can buy Yaki-Imo from the trucks to have them as a snack or serve with dinner at home.