Koulouri me Tyri is the sesame ring turned into something closer to a sandwich: a koulouri with cheese, either stuffed inside the ring or served alongside it. The plain koulouri is breakfast in one hand; adding tyri turns it into a small filled meal, and the cheese is doing real work rather than just riding along. This entry is about that pairing specifically, the ring as a structure for cheese, and how the structure either holds the cheese well or fights it.
There are two builds, and they behave differently. The split version: the ring is cut around its circumference, opened like a thin bagel, and cheese laid into the gap, often a salty white cheese, sometimes a firmer yellow one. The side version: the ring stays whole and the cheese is eaten next to it, torn bites alternating. Either way the koulouri should be fresh, because a stale ring makes a poor sandwich. Good execution means a ring with enough crumb to actually hold a filling without shattering, a clean split that does not crush the ring flat, and cheese in proportion to the bread rather than a thin smear lost under the sesame. Sloppy work shows as a ring split so unevenly it falls into two arcs, a dry day-old koulouri that crumbles the moment it is bent open, or so little cheese that the salt and the sesame never meet. The contrast that makes this work is the toasted, nutty sesame crust against a cool salty cheese, and that contrast collapses if either side is stale or stingy.
Variation runs along the cheese and the cut. A soft brined white cheese gives a tangy, almost creamy filling; a firmer cheese gives a drier, chewier bite that holds its shape better in the split. Some versions keep the ring whole and serve the cheese as a wedge for tearing and dipping, which is closer to a bread-and-cheese plate than a sandwich. The ham-and-cheese form and the sweet chocolate form build on the same split-ring idea and each deserves its own article rather than being crowded in here. The base ring itself, the plain Koulouri Thessalonikis, is the foundation everything here rests on and is covered separately.