Zhīma Shāobing (芝麻烧饼) is the plain sesame flatbread: a layered, flaky wheat round with a heavy coat of sesame seeds and no filling worked into it, baked or griddled so it can be eaten as bread or split open to hold something. This article covers the unfilled round, because its whole purpose is to be a structural shell other things are built on. The angle is restraint. Nothing is folded inside, so the bread stands entirely on its lamination and its sesame crust, and it is shaped deliberately so it can be cut and stuffed without crushing into paste.
The craft is in the fold, the seeds, and the bake. A wheat dough is rolled thin, brushed with an oil-and-flour roux, then folded and rolled through several turns so the fat sets many separate strata; the round or rectangle is shaped, the top wetted and pressed firmly into a dense layer of sesame seeds so they stick and toast, and it is baked against a hot clay-oven wall or griddled on one face and finished covered until the layers set crisp. The aim is airiness and structure at once. Done well the zhīma shāobing has a thin, shatter-crisp, sesame-studded shell, an interior of fine flaky sheets that pull apart cleanly, and enough internal space to be split and packed without compressing flat. Done poorly the failure modes are specific: skimp the oil lamination and it bakes into a dense solid bun with no layers; under-bake it and the center stays gummy and tears instead of flaking; over-bake or over-griddle it and it dries into a hard cracker that crumbles rather than holding a filling; under-press the sesame and the seeds shed the moment it is handled.
It shifts mostly by shape and by what it is built to carry. Round and rectangular forms sit side by side; a slightly richer dough flakes more delicately, a leaner one makes a sturdier wrap for stuffing. Left whole it is torn and eaten with congee or soy milk; split, it becomes the shell for a filled assembly. The egg-stuffed form, the pork-tenderloin form, the meat-baked-in ròu shāobing, and the sesame-paste zhīma jiàng shāobing each run on a different filling logic and deserve their own article rather than being crowded in here. What holds plain zhīma shāobing together is structural generosity: a layered, sesame-crusted shell made on purpose to be split and filled while staying crisp.