The Sandwich Farci Poitevin is built around a green terrine rather than a meat one. The farci poitevin is a Poitou preparation of leafy greens and herbs, chard, sorrel, spinach, lettuce, parsley and onion, chopped fine, bound with egg and a little fat, often wrapped in cabbage or chard leaves and cooked slowly until it sets into a firm, dark, sliceable loaf. Cooled, it cuts like a pâté, and that is how it reaches the sandwich: a thick slice of the set greens laid on buttered bread, with a pickle or a leaf alongside. What makes it its own thing is that the filling is a vegetable preparation that behaves like charcuterie, sliceable, savory, and made to be eaten cold.
The logic follows from the bind. Because the greens are held together with egg and cooked through, the farci keeps its shape under the knife and on the bread, which is the trait that makes it a sandwich filling at all; a loose braise of the same greens would never hold. It is deeply herbal and a little earthy, low in fat compared to a meat terrine, so the build adds back what it lacks: butter on the crumb to carry it, a cornichon or a sharp leaf for the acidic counter that keeps the greens from reading flat. It is eaten cold, like the terrine it resembles, so there is no warm component and no reason to wait. The bread wants a real crust and a tight crumb, because a thick slab of the farci needs something with structure under it and the slice gives up a little moisture as it sits.
The variations stay within the Poitou green-terrine idea rather than leaving it. The mix of greens shifts with what the season gives, more sorrel for a sharper edge, more chard for body; some versions work a little cured pork or fat back through the greens for richness, edging the farci back toward a true terrine; the cabbage-leaf wrap is sometimes kept on for the slice and sometimes not. The Sandwich Farci Poitevin belongs with the place-named sandwiches the catalog groups under Regional Specialty Sandwiches. Its specific contribution is a bound green terrine as the filling: a vegetable preparation engineered to slice and eat cold like the charcuterie it sits next to.