What heat does to the vegetable is the entire premise. Raw aubergine is spongy and bland; grilled or fried, it collapses into something silky, faintly smoky, almost meaty in the mouth. That transformation is the whole sandwich. Slices of aubergine cooked until soft and bronzed, salted while still warm, laid into a split crusted loaf. The move that lifts it from a plain vegetable build is a dark, briny counterpoint, most often a stripe of tapenade, the Provençal olive paste, smeared on the crumb so its salt and bitterness meet the sweet, oil-rich flesh.
The craft is managing oil and seasoning. Aubergine drinks fat as it cooks and gives much of it back as it sits, so the slices want to be cooked thoroughly, then rested and blotted so the sandwich is rich rather than wet. The flesh is also mild and slightly sweet on its own, which is the design problem: without a strong partner it reads flat. Tapenade solves it directly, salt and olive against the smoke; a little salt and a squeeze of lemon do a leaner version of the same job, lifting the sweetness so it does not sit heavy. The bread needs a real crust because the filling is soft and oil-bearing and brings no structure, and the sandwich is best eaten within a few minutes of assembly, before the oil works fully through the crumb.
Variations stay in the southern register. The same loaf takes the aubergine layered with roasted pepper and courgette into a cooked-vegetable build, the oil binding the three the way it binds a stew packed into bread; or a smear of fresh goat cheese under the tapenade for a creamy, tart counterweight; or a few basil leaves laid on the warm flesh so the herb opens against the heat. Each holds the bread and the restraint constant and changes only what sharpens the aubergine. The Sandwich aux Aubergines belongs with the plant-forward builds the catalog groups under Sandwich Végétarien. Its specific contribution to that shelf is a vegetable that turns rich and smoky under heat, asking the sandwich for a salt-and-bitter partner rather than a sauce.