The Sandwich Sardines Grillées is built around fresh sardines cooked over fire, not lifted from a tin, and that single fact reorganizes the whole sandwich. Fresh sardines grilled whole come off the heat meatier, hotter, and far less saline than the cured tinned kind: the flesh is firm and flaky, the skin charred and slightly bitter, the fish carrying smoke from the grill rather than oil from a can. They are boned and laid down the length of an Atlantic-coast loaf, split and lightly buttered or simply rubbed with oil, the rest of the build kept spare so the grilled fish stays in front.
The logic follows from the heat and the leanness. Because the sardine is grilled rather than packed in oil, it brings its own smoke and a clean savour but not the heavy salt and slick of the tinned version, so the sandwich leans toward brightness rather than restraint: a hard squeeze of lemon, a turn of black pepper, sometimes a few slices of tomato or a sliver of raw onion to set a cool, sharp note against the char. Butter is optional here in a way it is not with tinned sardines, since there is less salt to bridge; a thread of good oil often does the same work without muting the smoke. The constraint is timing. Grilled sardines are at their best hot or barely warm, the skin still crisp, so this is a sandwich built and eaten quickly, near where it was cooked, before the fish cools and the flesh tightens. The bread needs a real crust to hold flaky fillets and their juices without going slack.
Variations stay within the grilled and oily fish shelf rather than wandering off it. The tinned, oil-packed reading is its own sandwich, treated as the Sandwich aux Sardines, saltier and softer where this one is hot and clean; grilled mackerel is a meatier fish handled the same way; a build with tomato and onion pushes the bright counterpoint further against the char. Each holds the fresh, fire-cooked fish as the fixed point and changes only what cuts it. It belongs with the fish sandwiches the catalog groups under Baguette Poisson. Its specific contribution is a sardine cooked over flame rather than cured in a can, meaty and smoky enough that the sandwich tilts toward brightness instead of restraint.