Yèr Bā (叶儿粑) is the leaf-wrapped rice cake, a soft pillow of glutinous rice dough sealed around a sweet or savory filling and steamed inside a fresh leaf that scents the whole thing, the rice dough acting as the bread. The angle is the dough as an enclosing wrapper held by the leaf. This is a sandwich made of glutinous starch holding a core, and it succeeds or fails on getting a tender, chewy rice skin to seal a generous filling cleanly while the leaf keeps it from sticking and lends a green, faintly grassy fragrance. Get it right and you bite through a soft, slightly sweet rice shell into a hot center of sugared sesame or savory pork and pickle; get it wrong and you get a gummy or split lump that bleeds its filling and tastes only of plain paste.
The build is a wrapped-and-steamed parcel, not a folded or rolled one. Glutinous rice flour, sometimes cut with a little regular rice flour, is mixed and kneaded into a smooth, pliable dough, often tinted faintly green if a vegetable juice is worked in. A portion is flattened in the palm, a spoon of filling is set in the center, and the dough is drawn up and pinched closed into a smooth dumpling with no seam showing. The classic savory core is minced pork with preserved mustard greens, scallion, and ginger; the sweet core is brown sugar with toasted sesame or a sweet bean paste. Each parcel is set seam-side down on a piece of fresh leaf, a banana, ginger, or other broad leaf depending on the region, and steamed until the rice skin turns translucent and tender and the leaf perfumes it. Good execution shows a skin that is soft and chewy without being sticky-raw, a sealed parcel that held its shape and did not leak, a filling that is hot and well balanced, and a clean leaf scent through the whole bite. Sloppy work shows fast: underworked dough that steams up gummy and grey, an over-filled parcel that splits in the basket, too little steaming so the rice stays chalky at the center, or a dry leaf that sticks and tears the skin when peeled.
It shifts mostly by the filling and the leaf used to wrap it. The savory build leans on pork and pickled greens for a salty, slightly sour read; the sweet version drops the meat for sugar, sesame, peanut, or bean paste and pushes toward dessert. The choice of leaf, banana, ginger, reed, or other regional greens, changes the aroma and how the cake releases when unwrapped. The same glutinous-dough-sealed-and-steamed method underlies a broad family of leaf-wrapped rice cakes and sticky-rice forms, and yèr bā keeps its identity by being a soft pinched dumpling of rice dough, steamed inside a single fragrant leaf around a sweet or savory core.