At the grill stall this comes together around a hot coil of fresh coarse-ground pork sausage, cut to the bread and laid in still steaming. The saucisse de Toulouse is seasoned with little more than salt and pepper, sold in a rope rather than dried, and it has to be cooked, which is what makes this a warm sandwich rather than a cured one. The build is a split crusted loaf, the grilled sausage, a stripe of mustard, often a spoon of soft cooked onions.
What makes it work is the coarse grind against a real crust. The roughly chopped pork keeps its texture and gives off juice as it cooks, so the bread has to be firm enough to take that moisture without going limp. The crust holds while the crumb soaks just enough to bind everything. Mustard cuts the fat; the cooked onions, sweet from the same pan, round the plain pork and carry its juices across the bread. The sausage wants to be cooked through but pulled before it tightens, since one taken too far loses the loose juicy grain that is the whole reason to reach for it.
This is eaten in hand and warm, finished in the few minutes the sausage stays hot and the crust stays crisp. It belongs with the cured and prepared pork builds the catalog groups under Sandwich Saucisson & Charcuterie, and its contribution is plainness done right: a fresh sausage, a sturdy crust, and nothing competing with either.