The Sandwich Poulet-Curry is defined by a sauce, not by the chicken. The filling is cooked chicken bound in a curried mayonnaise: mayonnaise loosened and tinted with curry powder, sometimes a little crème fraîche, the meat diced or pulled and folded through until every piece is coated. That dressed mixture, not plain sliced breast, is what goes into a split baguette, and it is the spiced mayonnaise that makes this a distinct sandwich rather than a chicken baguette with seasoning. It is a standard option in the boulangerie cold case. The region is national.
The craft is in the bound mixture and what it solves. Plain cooked chicken breast in a sandwich risks reading dry and flat; folding it into a curried mayonnaise fixes both problems at once, the fat carrying moisture into lean meat and the curry supplying the flavor the bird lacks on its own. Because the filling is pre-mixed rather than layered, the assembly is simple and forgiving: the curried chicken is packed along the crumb, sometimes with a few cool crisp leaves or a little raw onion for contrast, and the sandwich holds together because the mayonnaise binds it into one mass instead of a stack. The constraint is the dressing itself. Too little and the curry is a faint dusting; too much and it slumps and soaks the bread, which is the usual failure of any mayonnaise-bound filling. The right amount coats without running. A fresh baguette with a real crust does the structural work, and the sandwich keeps better through a few cold hours than most because the chicken is sealed in fat, though it is still best within the day.
Variations turn mostly on the spicing and what rides alongside, a hotter curry in one kitchen, a sweeter one rounded with mango chutney or a few raisins in another, sometimes diced apple for a cool sharp note against the spice. The Sandwich Poulet-Curry sits next to the plain Sandwich Poulet it varies from, and belongs with the roast-and-sliced builds the catalog groups under Baguette Rôti / Bœuf. Its specific contribution is the curried mayonnaise, a bound and spiced filling that makes the chicken sandwich the deli's flavored option rather than its plain one.