Nutella turns the piadina into the dessert and after-school version of itself, and the heat is the entire trick. Spread onto a round straight off the plate, the chocolate-hazelnut paste does in seconds what it never does from the jar: it goes from a stiff spread to a loose, glossy, almost pourable filling, sinking into the soft crumb instead of sitting on top of it. The defining fact is that this build depends on serving warm. Cold, it is a stiff smear in a bland flatbread; warm, the plain, faintly savoury Romagnolo dough becomes a soft, slightly fatty shell that carries the molten hazelnut and keeps the sweetness from going flat and one-note.
Making it well is almost entirely about timing, because there is one ingredient and the bread. The dough is the standard Romagnolo build, flour with lard or oil and barely any leavening, rolled thin and cooked dry on a hot plate until it blisters in dark freckles and stays pliable, lifted before it crisps so it folds cleanly without cracking. The Nutella is spread thin and even onto the hot surface, not piled in a thick band, so it melts uniformly and grips the crumb rather than pooling and squeezing out at the first bite. Some cooks add a layer of sliced banana for body and a fresh edge against the sweetness, or a few crushed hazelnuts for crunch against the soft round. It is folded in half, often again into quarters for a child, and eaten at once while the filling is still flowing and the bread still warm.
The close cousins are one swap from here and stay sweet. There is the fruit-jam version with marmellata in place of the chocolate, the one built with Nutella and banana as its own established pairing, and the plainest fold dressed only with sugar melting into the warm round. Each is the same warm flatbread meeting a single changed sweet element, and each deserves its own article rather than being crowded in here.