The piadina con erbe di campo is defined by a bitter green tangle inside a plain flatbread, and by the fact that the greens are the filling rather than a garnish to it. Erbe di campo are wild field herbs gathered in the Romagnolo countryside, a seasonal mix that runs to dandelion, wild chicory, mild nettle tops, strigoli, and whatever else the season offers, cooked down hard with oil and garlic until they collapse into a dark, faintly bitter, mineral mass. The piadina is the unleavened flatbread, rolled thin and cooked dry on a hot plate until it blisters and stays pliable. The pairing is austere by design: the bread brings warm, plain starch and char, the greens bring all the savour and a clean bitterness, and a film of soft fresh cheese or a thread of oil is what binds the two so the parcel holds. Take the greens away and there is nothing to taste; serve them on a leavened roll and the flatbread's whole logic is lost.
The craft is in cooking the greens properly and not flooding the bread. Wild herbs are bitter and stalky raw, so they are wilted long and slow in oil with garlic and sometimes a little chilli until they are fully soft and their bitterness has rounded into something deep rather than aggressive; underdone they read harsh, overdone they go to grey paste. They must be drained well, because a wet filling soaks straight through an unleavened flatbread that has no crumb to absorb it. The piadina is rolled thin enough to fold without cracking and cooked just to char and pliability. A smear of crescenza or stracchino is often laid under the greens, not for richness but as a bind and a soft counter to the bitterness, sealing the surface so the oily filling stays put. It is folded and eaten warm, while the bread is still soft and the greens still have their edge.
The variations stay in Romagna and around the same flatbread, and each deserves its own article rather than being crowded in here. There is the version that adds a soft fresh cheese as an equal partner rather than a thin bind, the one with a cured meat laid against the bitterness, the cultivated-greens build using chard or spinach in place of the foraged mix, and the plain piadina alone. Each is a distinct balance struck against the same hot, pliable bread.