Roasted, not raw: that is the pepper this sandwich is built on. Bell peppers are blistered over heat until the skin chars and lifts, then peeled, sliced into soft strips, and dressed with olive oil before going into split bread. It is a national sandwich rather than a regional one, the roasted-pepper option a French counter offers among the vegetable builds. Roasting is the whole transformation: a raw pepper is watery and sharp, a roasted one is sweet, silky, and faintly smoky.
The craft turns on what the char does. Roasting drives off the pepper's water and concentrates its sugar, and peeling away the blistered skin leaves a soft strip that will not soak the bread the way raw pepper would. The oil the peppers sit in becomes the binder, so the bread needs a firm crust to hold it without going slack. The strips are layered rather than packed so the texture stays distinct, and the sandwich improves slightly as the bread takes up some of the oil. It is eaten cold or barely warm and keeps for a few hours, since the work is done once the peppers are roasted and dressed.
Variations stay in the cooked-vegetable register. A round of fresh goat cheese cuts the sweetness with a little tang; a smear of tapenade or a few anchovies push it toward the southern, brinier side; basil or garlic in the oil lifts it. The Sandwich aux Poivrons belongs with the plant-forward builds the catalog groups under Sandwich Végétarien. Its specific contribution is the roast: a pepper sandwich built on char and concentrated sweetness, not on the raw vegetable.