Yaki imo

Roasted sweet potato is a popular winter street food in East Asia and parts of Southeast Asia. In China, yellow-fleshed sweet potatoes are roasted in a large iron drum and sold as street food during winter. They are called kǎo-báishǔ in northern China, wui faan syu (煨番薯) in Cantonese-speaking regions, and kǎo-dìguā (烤地瓜) in Taiwan and Northeast China, as the name of sweet potatoes themselves varies across the sinophone world.

Source: Wikipedia