The panino con toma piemontese is a sandwich that turns on age. Toma piemontese is a semi-hard cow's-milk cheese from the Piedmontese mountains, and it is not one flavour but a span: a young toma is pale, supple, and mild, almost sweet and milky, while one aged for months firms up, dries toward the rind, and turns sharp, nutty, and pungent. The whole sandwich is decided by where on that curve the cheese is cut. A young wheel and an aged wheel are effectively two different fillings asking for two different sandwiches, and naming the panino after the cheese means naming a range, not a fixed thing.
The craft is reading the ripeness and building to match it. A young, soft toma is cut in generous slices or even pressed slightly into the bread, since it is mild enough to be the body of the sandwich and gentle enough to take a richer crust; an aged one is cut thinner and used with more restraint, because its sharpness and salt carry further and a thick slab reads as harsh. The cheese is served at cool room temperature so the texture and flavour actually open; cold from the fridge it is mute and waxy at every age. The bread is matched to the cheese rather than the other way round: a soft mountain loaf or plain roll for the mild young version, a more structured crusted bread for the assertive aged one. The counter follows the same axis, a little honey or fruit mostarda to play against a young sweet toma, a sturdier bread and a few walnuts to ground a sharp old one.
The named variations are mostly the age axis made explicit. There is the young toma build with honey, the aged version with walnut or mostarda, and the warmed panino where light heat softens a younger wheel into the crumb. Its Piedmontese neighbours, the castelmagno and the raschera, follow their own logic and deserve their own articles rather than being crowded in here.