Ka'ak (كعك) is the Lebanese street bread that doubles as a sandwich shell: an oblong, purse-shaped or handbag-shaped loaf, slightly sweet, with a chewy crumb and a crust crusted in sesame seeds, sold from glass-fronted carts and bicycle racks and filled to order. The angle here is that the bread is the point. Unlike a baguette or a pita that mostly stays out of the way, ka'ak carries its own flavor, the toasted sesame and a faint sweetness, and its own architecture, a hollow or a fold built to take a filling. Everything that goes inside is chosen to play against that sesame-and-sweet base rather than to ignore it.
The bread itself is what most of the craft sits in. The dough is enriched and lightly sweetened, shaped into the distinctive elongated ring or purse with a thinner band and a wider belly, proved, then coated densely in sesame before baking so the whole exterior toasts to a nutty crust. Fresh from a good cart it is soft and pliant with a tender chew and a fragrant, just-toasted sesame shell; left too long it goes dry and stiff, which is why vendors warm it on a small griddle or hot plate before filling. To serve, the wider end is split open or the loaf is sliced to make a pocket, and the chosen filling is spread or tucked inside, often with the bread given a quick reheat so the crust crisps and any cheese inside softens. A good ka'ak is warm, faintly sweet, and nutty with sesame, soft enough to fold without cracking; a poor one is cold, hard, and stale, the sesame gone flat, so that no filling can rescue it.
What goes inside is the whole variable, and the fillings each become their own named sandwich. The classic is a smear of za'atar and oil painted into the warm pocket; close behind are white cheese, labneh, a halved hard-boiled egg, halloumi, and akkawi, each turning the same bread into a distinct breakfast or snack. A sweet line exists too, chocolate spread being the obvious modern one, leaning on the bread's own sweetness. The bread also stands on its own, eaten plain and warm with nothing in it, which is the cleanest demonstration of why it works: a sesame-crusted, faintly sweet loaf good enough to be the whole snack before it is ever filled.