Char siu bao are the soft white buns at the front of every yum cha trolley. The dough is enriched and lightly sweetened so it steams up cloud-white, and the filling is diced barbecue pork bound in a thick oyster sauce gravy.
Two rules decide whether they work. The filling must be cold before it touches the dough, and the lid stays on for the full steam. Lift it early and the buns sink and wrinkle.
