The piadina romagnola is the flatbread itself, before anything is folded into it, and it is the reference every other piadina build is measured against. It is a thin unleavened round of wheat flour worked with fat, water, and salt, rolled out and cooked dry on a hot flat surface until it blisters in pale brown patches and stays pliable enough to fold without cracking. Nothing is laminated, nothing is proofed, nothing rises. The whole identity of the bread sits in three decisions: which fat, how thin, and how hot the testo. Get those right and the round is supple, faintly savoury, and strong enough to carry a filling in the hand. Get any of them wrong and it is either a cracker or a damp disc, and there is nowhere for the error to hide because there is nothing else in it.
The craft is the dough and the heat, because that is all there is. The flour is soft wheat, the fat is strutto, the rendered pork lard that gives the classic Romagnola round its short, tender bite, though good oil makes a lighter version with a cleaner snap. The dough is worked just enough to come together smooth, rested so the gluten relaxes and the round rolls out without springing back, then taken to a thickness that is a regional argument in itself: thicker and softer toward Cesena and the inland hills, thinner and crisper toward Rimini and the coast. It is cooked on a testo, the flat terracotta or metal plate, hot enough that the surface sets and freckles fast while the inside stays steam-soft, and it is pricked or pressed so it does not balloon. A good piadina comes off the heat flexible and is folded warm; a sloppy one is rolled unevenly, cooked on a cool plate so it dries out before it colours, and folds into a crumbling seam.
The variations are the fillings and the regional thickness rather than other breads, and each is its own build on this same base. There is the thin coastal round folded around squacquerone and rocket, the version filled with grilled vegetables, the loaded mixed fold, and the inland thicker style closer to a soft bread than a crisp one. Each of those is the same Romagnola round with one decision changed, and each deserves its own article rather than being crowded in here.