Which state the chèvre is in decides everything else, because the same goat's-milk cheese makes three different sandwiches depending on how far it has dried. Fresh chèvre is soft, bright, and spreadable, almost like a tangy curd; a half-aged log has firmed into a sliceable paste with a wrinkled rind and a sharper bite; a fully aged round is dry, dense, and pointed. The tang runs through all three and is the constant. The build is a length of baguette or a slice of seeded bread, often toasted, with the chèvre either spread across the crumb when fresh or laid in rounds when firm.
The logic follows from how far the cheese has dried. Fresh chèvre binds the sandwich itself, so it works smeared thick with nothing more than a drizzle of honey and a turn of pepper, the soft acidity carrying the bite. A firmer log is a layer rather than a spread, and it wants a partner with some weight: honey and walnut is the standard pairing, sometimes a leaf of bitter green, sometimes a film of fig to set against the sharpness. The tang is the load-bearing flavor at every stage, and the discipline is to give it a single sweet or bitter counterweight rather than a crowded one. Toasting the bread is common because warmth softens a firm round at its edges while the center stays cool and tangy, and it pulls a fresh spread slightly into the crumb.
The bread needs a firm crust and an open crumb to hold a cheese that is either soft enough to soak in or dry enough to shed, and the chèvre is best a little below room temperature so its tang stays sharp rather than turning flat.
Variations are mostly a matter of which named goat cheese carries it and at what age: a Sandwich au Chabichou for a chalky Poitou log, a Crottin de Chavignol for a small dense Loire round, a Sainte-Maure for an ashed log with a longer finish. Each is the same goat tang met in a different shape and a different state of drying. It belongs with the cheese sandwiches the catalog groups under Baguette Fromage, and its specific contribution is a cheese whose place on the fresh-to-aged scale changes whether it spreads or stacks.