The Sandwich Sud-Ouest is a regional register pressed into a baguette, and the register is duck. The South-West of France is duck country, and the sandwich that carries its name reaches for that shelf: slices of magret, the seared duck breast left pink; shreds of confit de canard, leg meat cooked and preserved in its own fat; a film of duck rillettes; and, when the build wants to announce itself, a smear of foie gras. Around it sits the rest of the regional pantry, a slice of jambon de Bayonne, a leaf or two, sometimes a spoon of fig or onion confit for a sweet counter. The bread is a real baguette with a true crust, because everything it carries is rich.
The craft is in managing richness with structure and a single sharp note. This is a sandwich where the filling brings its own fat in every form, magret through its cap, confit through its preserving fat, foie gras as nearly pure richness, so the design problem is not how to add flavor but how to keep the richness from going heavy and flat. The South-West kitchen answers the way it answers on the plate: a baguette with enough crust to cut the softness, and one acidic or sweet counterweight, a cornichon, a leaf of frisée, a spoon of fig confit, doing the job a glass of Madiran does at the table. The duck wants to be sliced thin and laid in shingles rather than slabbed, because at full thickness the fat turns waxy in the hand. It is best a little cool but not cold, since cold mutes the duck fat and the foie both, and assembled close to service so the bread stays firm under the load.
Variations stay inside the regional shelf rather than wandering off it. A magret build is the leanest and most direct, the seared breast carrying the sandwich nearly alone. A confit version is softer and deeper, the shredded leg meat reading almost like a rich spread. A foie gras build is the special-occasion reading, mi-cuit and filmed on with a little fleur de sel, the bread doing all the structural work. Each is a swap of one South-West preparation of the same bird for another, the crust and the single counterweight held constant. It belongs with the roast and beef sandwiches the catalog groups under Baguette Rôti / Bœuf, and its specific contribution is the South-West pantry condensed into one loaf, where duck in its several forms is the whole argument and the bread's job is to keep it honest.