The Christmas sandwich is the roast dinner folded into bread, and that is meant precisely rather than loosely. It is not turkey on its own between slices but the whole plate compressed: roast turkey, a slab of stuffing, a stripe of cranberry sauce, and in the fullest version pigs in blankets laid in alongside, all built into bread the day after the meal or, in its shop-bought form, sold as a deliberate miniature of it through December. The defining fact of this build is that every component is doing the job it did on the plate, only without a fork. The cranberry is the gravy substitute and the acid that cuts the meat; the stuffing is the savoury, herby ballast; the turkey is the cold, slightly dry centre the other two exist to rescue.
The craft is moisture management around a meat that has nothing left to give. Roast turkey reheated or, more often, gone cold from the fridge is lean and dries to rope between bread, so it is sliced thin and against the grain and, crucially, never left to carry the sandwich alone. Stuffing is the structural ally as much as a flavour: a sage-and-onion slab holds shape, adds the fat and salt the bird lost, and stops the filling reading as dry. Cranberry sauce supplies the lubrication and the sharp counter the gravy did on Christmas Day, applied as a measured stripe because a flood of it bleeds sweet-red into the crumb and turns the base to pulp. The bread needs real structure for a heavy, multi-layer filling, a sturdy white or a bloomer rather than soft sliced, and butter or a thin smear of the cranberry seals the bottom slice against the sauce. Pigs in blankets, when they go in, are split lengthways so they lie flat and the sandwich still closes; a layer of cold bread sauce or a few sprouts shredded in is the maximalist's full-plate reading.
The variations are the same leftover-plate logic with a different bird or trimming foregrounded. Roast chicken stands in for turkey out of season; ham off the Christmas joint with mustard is the savoury alternative to the cranberry build. Brie added to the turkey and cranberry is the festive café version, sausage and stuffing without the bird is the budget one, and a hot-pressed turkey-and-stuffing toastie is the warm reading. Each deserves its own article rather than being crowded in here.