Paninaro style names a sandwich read through a Milanese youth scene rather than a recipe. The paninari were a fast-food subculture built around the commercial sandwich bars of central Milan, and the sandwich that defines them is the stuffed bar panino of that world: a soft round roll, often a sesame bun, loaded well past the Italian instinct for restraint. Where the traditional panino names one cured meat and stops, this one is deliberately full, layering cooked ham or a burger-style patty, melted cheese, lettuce, tomato, and a sauce. The defining fact is the maximalism: this is the Italian sandwich consciously borrowing the logic of an American counter and piling the roll high.
The craft is making a stacked, wet build hold together in a soft roll. The bun is chosen sturdy enough to take heat and moisture without dissolving, sometimes lightly toasted or warmed so it firms against the filling. The cheese is a melting one, laid on warm so it slackens and binds the layers rather than sliding out as a cold sheet. The sauce, often a mayonnaise-based dressing or a tomato-and-mayonnaise blend, is structural as much as flavour, gluing the lettuce and tomato to the meat so the whole thing survives the first bite. The lettuce and tomato are the cool, crunchy counter to a rich, melted centre, the same balancing role the pickle plays on a burger. It is built to order and eaten fast, before the warm cheese sets and the sauce works its way into the crumb.
The variations are the bar menu of that scene and the modern paninoteca that inherited it: the ham-and-melted-cheese build, the patty version with lettuce and sauce, the doubled stack, the contemporary chef's reading that keeps the fullness but raises the parts. Each is the same maximal, sauced, melted roll argued with a different filling, and each deserves its own article rather than being crowded in here.