The panino con pane casereccio is the sandwich where the bread is named first because the bread is the point. Pane casereccio, the generic country house loaf, is a large rustic wheat bread with a thick chewy crust and an open, slightly sour, faintly tangy crumb, the loaf a baker pulls out by the kilo rather than the roll. As a carrier it does not disappear under a filling the way a soft white roll does: it asserts a structure of its own, a crust that resists the teeth and a crumb that holds its shape against oil and moisture. That assertiveness is the whole sandwich. It is the bread chosen precisely when the filling is a strong cured meat or a hard cheese that wants something with its own weight to push against rather than a blank.
The craft is in the cut and in matching the filling to a loaf that fights back. A pane casereccio is sliced thick, often hand-torn rather than machine-cut, so each piece carries a band of crust and a generous depth of crumb; cut thin it loses the point and behaves like ordinary bread. The crumb's open holes are a feature, catching a thread of olive oil or the rendered fat of a warmed salume without going to paste, while the crust keeps the whole thing rigid enough to eat standing. The filling stays singular: a few slices of one cured meat, a wedge of one sharp cheese, oil only where it bridges a very lean filling to a dry crumb. The loaf is robust enough to hold for a few hours without collapsing, which is the practical reason it is the everyday choice at a counter that builds ahead.
The named directions are really the regional country loaves the term covers. There is the dense Tuscan unsalted version that reads flat and is built for salted fillings, the pane pugliese of the South with its deep gold crust, and the dark pane casereccio integrale worked with wholemeal for a heavier, nuttier bite. The protected Altamura loaf is a stricter, denser thing entirely and stands apart. Each of these breads sets its own rule for how wet a filling may be, and each deserves its own article rather than being crowded in here.