The Sandwich Pâté de Campagne is built on the coarsest, most forthright pâté in the French repertoire and a single sharp thing to cut it. Pâté de campagne is country pâté in the literal sense: pork shoulder and liver ground rough rather than smooth, seasoned hard with pepper, often laced with brandy and bay, set firm enough to slice in a thick slab rather than spread. On a buttered crusted baguette it goes down in one or two generous slices, with a few cornichons and sometimes a leaf or two of frisée, and that is the whole sandwich. It does not need a recipe so much as a charcuterie within walking distance.
The craft is the management of richness, and the cornichon is the load-bearing element. A thick slab of country pâté is fatty, peppery, and relentless on its own; the vinegar of the cornichon is the thing that resets the palate between bites and keeps the sandwich from turning leaden by the middle. The butter is not redundant despite the pâté's own fat: it bridges the meat to the crust and carries a little salt across the wheat. The bread has to bring a real crust because a coarse pâté gives the sandwich no structure of its own, only weight. Get the proportions right, pâté generous, acid present, crust firm, and it is a complete portable lunch; get them wrong and it is the sandwich you regret in the middle of the afternoon. It eats cool and clean, the pâté firm, the pickle cold against it.
Variations stay on the charcutier's shelf rather than wandering off it. A more liver-forward pâté pushes the savor deeper and wants a touch more acid to balance; a Breton-style coarse pâté brings more pepper and a denser grind; a smear of mustard can stand in for or join the cornichon as the sharp counter. The frame is fixed across all of them: a coarse country pâté, a buttered crust, one acidic thing to keep it honest. It belongs with the charcuterie sandwiches the catalog groups under Baguette Pâté, and its specific contribution is the plainest expression of the form, a rough-ground pâté that asks only for bread, butter, and a pickle and rewards exactly that restraint.