Sheep and goat, not cow, is what fills this bread, and that one fact shapes everything that follows. The island's wheels run pungent and salty: a young brocciu, the soft fresh whey cheese, is mild, milky, and almost spoonable, while an aged Corsican tomme or a vieux Corse is firm, sharp, and carries the slightly wild, herbal note that comes from animals grazing the maquis. The sandwich is a split crusted loaf and one of these cheeses, treated according to how soft or hard it is. What lifts it above a generic cheese-on-bread is the character of the milk: these are not gentle cow's-milk pastes, so the sandwich frames an assertive, regional flavor rather than a neutral one.
The build follows the cheese's state. Fresh brocciu is soft enough to spread and mound, needs no butter, and wants a firm crust to give it the structure it lacks. An aged tomme is sliced and laid in shingles, and a film of butter or a little olive oil bridges its salt and sharpness to the wheat. The discipline is restraint: a strong Corsican cheese does not need a competing condiment, and piling one on means tasting the addition instead of the cheese. The sandwich is eaten cold and soon, the cheese at room temperature so its flavor opens, the bread fresh enough that its crust holds against a moist or oily paste.
Variations stay on the island's shelves. The same bread takes the soft fresh brocciu on one day and a hard, sharp aged tomme on another; a stripe of fig jam or chestnut honey is a common single sweet note against the salt, and a leaf of mint sometimes goes in with the fresh cheese in the island manner. A slice of Corsican charcuterie laid alongside turns it toward a mixed build. The Sandwich au Fromage Corse belongs with the cheese builds the catalog groups under Baguette Fromage. Its specific contribution to that shelf is the maquis: sheep and goat cheeses carrying a wild, herbal sharpness that makes the sandwich taste of the island it came from.