The Chinese street food that is a steamed bun filled with pork is baozi.
Baozi is a yeast-leavened wheat-flour bun made by wrapping dough around a filling and steaming it. Pork is one of the most common fillings, although baozi can also contain beef, chicken, vegetables, tofu, sweet bean paste, or custard. The buns range from small snack-sized portions to large breakfast buns.
The word baozi means a filled bun in modern standard Chinese. This helps distinguish it from mantou, which generally refers to a plain steamed bun without filling. Xiaolongbao is a related but more specialized type: it usually has a thin wrapper and a soup-rich filling formed from gelatin that melts during cooking.
Baozi has a long history in Chinese food culture. Earlier sources used mantou for some filled buns, but terminology gradually became more distinct. Today, baozi is eaten throughout China and is also familiar abroad through dishes such as char siu bao and Filipino siopao.