The Sandwich Falafel is built around a fritter that has to be eaten hot from the fryer or it is not worth making. The falafel is a ball of ground chickpeas, herbs, garlic, cumin and coriander, deep-fried so the outside goes to a hard, cracked shell and the inside stays green and steaming, and the sandwich is several of them crushed into bread with the things that cut their richness: shredded cabbage or salad, pickled turnip and cucumber, a fried slice of aubergine often, and tahini sauce poured over until it runs. In France it is street food in the Levantine-into-Maghrebi register, packed into a folded pita or, as the model has it, into a split baguette when the stand works off the French loaf. What makes it its own thing is the contrast of that brittle hot crust against everything cold and sharp pressed around it.
The logic is heat against acid against fat. The fritter is dense and oil-rich straight out of the fryer, so the build loads acidity and crunch opposite it: the sharp pickled turnip, the raw cabbage, a squeeze of lemon, the cool tahini that ties the whole thing together and keeps the chickpea from reading as dry. Timing is the discipline, because a falafel that has sat goes leaden and the shell softens to the texture of the inside, which is the difference between a good stand and a bad one. The bread is structural and absorbent at once: a pita pocket holds the loose pile together while soaking the tahini that escapes, and the baguette version trades the pocket for a crust that has to be sturdy enough not to give way under sauce. Either way it is assembled fast at a counter, eaten standing or walking, and best within a few minutes of frying.
The variations are the stand's small adjustments rather than a codified set. Harissa or a chili sauce goes in for heat, pickled chilies for a sharper one, extra fried aubergine for body, the sauce switched from tahini to a garlic-white sauce on the stands that also turn a spit. The Sandwich Falafel belongs with the urban street sandwiches the catalog groups under Sandwich Grec / Kebab. Its specific contribution is the fried chickpea fritter as the core: a sandwich whose quality is set by how recently the falafel left the oil.