The Tuscan salame in this panino is named for the fact that it falls apart. Sbriciolona, from sbriciolare, to crumble, is a coarse-ground, fennel-seeded salame cured soft and loosely packed so it will not hold a clean slice: cut it and it breaks into a rubble of meat and fat rather than a tidy round. That defect is the whole character. The crumble means the salame distributes itself across the bread instead of sitting as a disc, every bite carrying fat, lean, and the sweet anise hit of the fennel seed at once. The bread is plain because the salame is already doing three things; a loud loaf would only get in the way.
The craft is working with a meat that refuses to behave. Because sbriciolona will not slice thin and clean, it is cut thick and a little rough, or even pressed and torn, and then laid generously so the crumble fills the bread rather than perching on it. The fennel is the signature and is protected: nothing sharp or sweet is added that would mask it. The bread is the classic Tuscan match, an unsalted pane toscano or a schiacciata, the saltless crumb deliberately bland so it lets the salame's salt and fennel come forward rather than competing. A thread of oil appears only where the bread is very dry. It is built to be eaten soon, while the fat is still soft and the crumble has not dried at the cut face.
The variations are mostly about the bread and the cut rather than the salame itself. There is the version on warm schiacciata so the heat slackens the fat, the one pressed flat so the crumble compacts into the crumb, and the related fennel-cured Tuscan salami, finocchiona chief among them, which is the firmer, sliceable cousin of the same idea. Those deserve their own articles rather than being crowded in here.