Báobǐng (薄饼) is the thin wheat pancake wrapper, not a sandwich in itself but the pliable round that turns roast duck and a handful of fillings into one. This article treats the báobǐng on its own terms, because everything a diner does at the table, the spreading, layering, and rolling, depends entirely on the qualities baked into this plain, almost translucent disc. The defining trait is a paradox the cook has to engineer: it must be thin enough to disappear against the filling, yet strong and supple enough to roll tight without tearing or going wet.
The craft is in the dough and the cooking surface. A soft, well-hydrated wheat dough is rested so the gluten relaxes, then a common method pairs two thin rounds with a film of oil between them and cooks the doubled disc on a dry griddle; the oil layer lets the two halves peel apart afterward into wrappers thinner than either could be cooked alone. Heat is kept moderate so the pancake stays pale and flexible rather than browning into a stiff crepe. Good báobǐng is barely colored, soft enough to fold without cracking even after it cools a little, and just sturdy enough that a load of duck, scallion, and sauce can be rolled without splitting the seam. The failure modes are easy to read: cooked too hot or too long, it dries to a brittle sheet that fractures the moment it is rolled; underworked dough makes a thick, doughy round that smothers the filling; rolled too far in advance without cover, it dries at the edges and curls.
From there it shifts mostly by thickness, size, and how it is kept warm. The version paired with Peking duck is small and very thin, sized to one or two folded bites, while wrappers for other rolled dishes run larger and a touch sturdier to hold a bulkier filling. Steaming rather than griddling gives a softer, moister wrapper some kitchens prefer for richer fillings, and a basket kept covered at the table is the quiet detail that keeps a stack from drying out mid-meal. The point of the báobǐng is structural neutrality: it contributes texture and a vehicle, not flavor, so the duck skin, sweet bean sauce, scallion, and cucumber read clearly. Where it is rolled around roast duck, that assembly is its own preparation and deserves its own article rather than being crowded in here.