Ka'ak b'Halloum (كعك بالحلوم) is the sesame street bread filled with halloumi, and the angle is what a firm grilling cheese does inside a shell that is itself gently sweet and nutty. Halloumi does not melt and run the way soft white cheeses do; warmed, it softens, browns slightly, and keeps its shape, holding a squeak even after heat. That makes it a clean match for ka'ak, because the bread is reheated to crisp its sesame crust anyway, and the cheese can ride that same warming without collapsing into grease. The result is a substantial breakfast sandwich where the cheese stays a distinct, salty, slightly chewy band against the faintly sweet crumb.
The build is straightforward and the discipline is in the slicing and the salt. The ka'ak is warmed so the crust re-crisps and the inside loosens, then opened along its wider belly. Halloumi is sliced into slabs or grated and laid inside, sometimes briefly griddled or pressed so it takes a little color before going in, sometimes just tucked in and warmed with the bread. Because halloumi is salty straight from its brine, the bread's own mild sweetness helps, but kitchens still balance it with tomato, mint, or a measure of za'atar and oil to add acid and aroma against the salt. The judgment calls are thickness and heat. Too thick a slab and the center stays cold and rubbery while the crust overcooks; too long against the heat and the cheese turns tough and the salt becomes punishing. A good ka'ak b'halloum has a crisp sesame shell, a soft and yielding cheese that still has chew, and enough tomato or herb to keep the salt in check; a poor one is bland and rubbery or aggressively saline with a stale loaf around it.
It varies by what is added with the cheese and by how the halloumi is handled. Za'atar and oil, tomato, mint, cucumber, and olives are the usual partners, each rounding it into a fuller breakfast. Some versions grill the cheese hard for a browned, almost crusted slice; others keep it barely warmed and soft. Within the ka'ak family it sits alongside the akkawi, labneh, egg, and za'atar fillings as the firm-cheese member, distinct from the soft-cheese forms because halloumi browns rather than oozes. It is essentially the Levantine habit of eating grilling cheese with bread and tomato, folded into the sesame loaf and warmed so the crust and the cheese come up together.