The Sandwich Lentilles du Berry is built on a lentil salad, and the lentil is the whole point. The lentille verte du Berry is the small green lentil of the Berry, firm-skinned and holding its shape after cooking rather than breaking down, with a clean, faintly peppery, earthy flavor. Dressed cool as a salad with vinaigrette, shallot, and herbs, then laid into bread, it gives the sandwich a textured, savory filling that does not need meat. The build is a crusted loaf, often split and lightly buttered, packed with the dressed green lentils and a few sharp accents. The defining element is the lentil itself, a salad with enough body and bite to be the reason the sandwich exists.
The logic follows from how the lentil behaves. Because the Berry lentil stays whole and firm, the salad has structure the way a grain salad does, so it sits in the bread as distinct beads rather than collapsing into a smear, and you taste it in clean bites. The vinaigrette is doing double work: it seasons the lentil and it supplies the acidity that keeps an earthy, starchy filling from going flat or heavy. The constraint is moisture and structure, because a wet dressing can soften a soft loaf, so the bread needs a real crust and a firm crumb to stay distinct against the salad. The filling brings flavor and texture but no binding, so the loaf has to hold it; a shallot bite or a leaf of something green keeps it lively. Dressed and eaten reasonably soon, while the crust still has bite and the lentils sit just below cool, it holds as a clean vegetarian sandwich.
Variations move along the salad's seasoning and what is laid in with it. A mustard-sharpened vinaigrette for more bite, walnuts or a firm cheese for body, a few herbs or pickled shallots for lift, a smear of fresh cheese to bind. Each is a recognizable adjustment of the same green-lentil-salad idea, the Berry lentil and the firm bread held constant. It belongs with the plant-forward builds the catalog groups under Sandwich Végétarien, and its particular contribution to that shelf is a regional lentil that holds its shape, a salad with the body to be the filling rather than a side to one.