The panino toscano is defined by a deliberate blandness in the bread and a loud, fennel-sweet salame against it. Pane toscano is baked without salt, so the crumb tastes of little more than wheat and crust. That saltlessness is the whole design, because the classic filling is finocchiona, a soft pork salame heavily seeded with wild fennel and cured rich and fatty, and a pecorino toscano whose salt and sheep tang would fight a salted loaf. The unsalted bread is built to disappear so the salame and the cheese carry every note of salt, fat, and anise. Salt the bread and the filling has nowhere to land; take the finocchiona away and the loaf reads as undersalted toast.
The craft is matching a flavourless crumb to a filling that has to do all the work. Finocchiona is cut thick rather than shaved, because cured soft it tends to break at the slice, and a generous, slightly rough cut lets the fat and the fennel spread across the dry crumb instead of perching as a tidy round. The pecorino is the young, supple kind shaved thin so it bends into the bread, or a sharper aged wedge slabbed thicker when it stands alone. The bread is the test: a good loaf has a thick, almost biscuit-hard crust and an open, chewy inside that drinks the salame fat without going to paste. A thin thread of Tuscan oil appears only where the crumb is very dry, never as a dressing, because the finocchiona already brings the fat. It is built to be eaten before the cut face of the salame dries and stiffens.
The variations stay in Tuscany and mostly change the salume or the cut. There is the version built on sbriciolona, the crumblier cousin of finocchiona that falls apart rather than slices, the one with a Tuscan prosciutto cured saltier and leaner against the same bland bread, and the build that drops the meat for a wedge of aged pecorino with a smear of chestnut honey. Each pulls the unsalted-bread idea somewhere distinct enough that it deserves its own article rather than being crowded in here.