The Piave is a cow's-milk cheese from the Veneto, and what makes a panino of it interesting is that the cheese is really a range rather than a single thing. It is sold by age, and the age is the whole sandwich: fresco at a few months is pale, springy, mild and faintly sweet; mezzano firms up and the nuttiness comes forward; vecchio and the longest-aged Riserva go hard, deep gold, granular and sharp, closer in bite to a Parmigiano-Reggiano than to the soft young wheel it started as. Choosing where on that line to cut is the decision the panino is built on, because a young Piave and an old one make almost opposite sandwiches.
The craft is matching the cut to the age and letting the bread stay quiet. A young Piave is sliced, soft enough to fold a little against the crumb, sweet enough that it wants almost nothing with it; an aged one is better cut thick or broken into shards so it crumbles across the bite the way a hard grating cheese does, and it can take a drop of aceto balsamico or a few drops of honey without being overwhelmed. The bread is plain on purpose: a wheel at its right ripeness is loud enough that an assertive loaf would only fight it, so a clean white roll or a close-crumbed country bread does the carrying and gets out of the way. Assembly is simple because a single cheese chosen at the right point on its own age curve is already a finished idea.
The Veneto and the wider Alpine arc keep a long shelf of these cow's-milk wheels, and each is its own subject rather than a version of this one. There is the Asiago in its fresh and aged forms, the Montasio of Friuli, the Monte Veronese, and the gentler young-Piave hands that pair it with pear or fresh figs. Each is one wheel, at one age, given a bread, and each deserves its own article rather than being crowded in here.