Turkey and stuffing is the Christmas-leftover sandwich defined by sage and onion rather than sweet fruit, and the stuffing is the lead, not a side. Cold roast turkey goes onto bread with a layer of sage-and-onion stuffing pressed against it, and that herby, savoury, slightly crumbly mass is what names the sandwich and carries it. Where the cranberry version solves cold turkey with a bright sharp sauce, this one solves it with seasoning and moisture from the stuffing itself: the onion sweetness, the sage, the fat and salt the stuffing absorbed in the roasting tin all transfer to the meat and put back the savour the cold breast lost overnight. The turkey supplies the body; the stuffing supplies the flavour and most of the reason this sandwich exists.
The craft is making a crumbly, dry-ish component behave as a layer. Stuffing out of the fridge is firm and prone to falling apart, so it is sliced or pressed into a slab thick enough to hold rather than scattered loose, where it would shed out of the sides at the first bite. It brings savour but not much moisture of its own once cold, so the build usually needs a wet element alongside it, a smear of mayonnaise, a little of the cranberry, or bread sauce, to keep a sandwich of two dry-ish things from reading as dry on dry. The turkey is sliced thin and against the grain and laid loose so it stays tender against the firmer stuffing. Butter to the edges seals the crumb and bridges the salt across, and the bread is plain and soft, a white or a light wholemeal, since there is no heavy fat to fight and the stuffing is already the textural event.
The variations are the rest of the Christmas plate arranged around the sage-and-onion core. Adding cranberry brings the sharp-sweet counter and shifts the sandwich toward the fruit-led reading; pigs in blankets or a slice of gammon push it toward a full festive stack; bread sauce layered with the stuffing doubles the soft savoury element; a peppery leaf cuts the richness. The cranberry-led version, where sweet-tart fruit rather than sage is the defining note, is a separate sandwich. Each deserves its own article rather than being crowded in here.