Jiānbing with Hēi Zhīma (煎饼黑芝麻) is the jianbing finished with black sesame seeds scattered onto the crepe, a small, deliberate addition that puts a toasted, faintly bitter note over the standard street-crepe base. The angle is a single seasoning change and the line it draws. The seeds add no structure and no real bulk; their entire job is aromatic, a roasted nuttiness and a faint bitterness laid across the savory-sweet sauce and the egg so the wrap gains a top note it otherwise lacks. Get it right and the sesame reads as a clean perfume over each bite without crowding the sauce. Get it wrong and the seeds are either invisible or, raw and over-scattered, turn the wrap dusty and faintly soapy.
The build is the familiar jianbing routine with sesame as the finishing step. A thin mung bean and wheat batter is spread on a hot griddle into an even circle, an egg is cracked on and smeared flat to bond into the crepe, and the disc is turned and painted with sweet fermented flour paste, tiánmiànjiàng, a fermented bean or sesame note, and chili sauce. Chopped scallion goes on, and the black sesame is sprinkled across the sauced surface while it is still tacky so the seeds stick rather than fall away in the fold. A crisp interior, a thin deep-fried cracker, báocuì, or a length of fried dough stick, yóutiáo, is laid in, and the crepe is folded into a hand parcel. Good execution shows the sesame toasted, evenly but lightly distributed, and pressed into the sauce so it holds and releases a roasted aroma through each bite while the crisp core and the sauce still lead. Sloppy work is specific: raw, untoasted seeds that taste flat and chalky, a scatter so heavy it muddies the sauce and goes bitter, or seeds laid on a dry patch so they shed out the open end before the first bite.
It shifts mostly by how the sesame is treated and by what else is on the crepe. Pre-toasted seeds give a deeper, rounder note; a lighter hand keeps it a background perfume; some vendors fold the sesame into the batter instead so it speckles the whole crepe rather than sitting on the surface. The crisp interiors, báocuì and yóutiáo, are components with their own articles, and double-egg, ham-added, and heavier-chili builds each define a further named variant. Those each deserve their own treatment rather than being crowded in here, while this entry stays on the black sesame and the toasted top note it lays over the standard jianbing.