Roast pork and stuffing is the cold pork sandwich led by the sage and onion rather than by the meat, and the stuffing is what defines it. Cold roast pork on its own is mild and a little flat, a faintly sweet meat with set fat and no aromatic of its own once it has cooled. A layer of sage and onion stuffing changes the whole reading: the sage brings a resinous, slightly bitter herb note and the onion a sweet savoury depth, so the sandwich tastes seasoned the way the roast tasted on the plate rather than like cold meat between slices. The stuffing also brings a soft, crumbly, well-salted body that fills the bread more generously than thin pork alone. The pork is the meat; the stuffing is the flavour and half the substance, and it is the part that tells you which roast this came from.
The craft is in the stuffing's texture and the bread that carries it. Stuffing wants to be moist enough to bind and hold a slice without crumbling away, but not so wet that it slumps and soaks the loaf, so it is pressed firm and cut rather than spooned in loose. The cold pork is sliced thin and against the grain so it stays tender beside the soft stuffing rather than going dense and chewy. This is a sandwich that suits a soft floured bap as much as a sturdy loaf, because the bap is yielding and faintly sweet and meets the stuffing rather than fighting it, and it is the form this build most often takes at a fete or a hog roast stand. Butter to the edges bridges the salt and keeps the crumb from going to paste under a moist filling.
The variations are mostly a question of what shares the bread with the stuffing. A stripe of sharp apple sauce alongside cuts the fat and lifts the sage; crackling tucked in adds the snap the soft build otherwise lacks; the full festive version runs stuffing with the Christmas trimmings. The plain cold-pork slice with no stuffing is a thinner, blanker reading. Each deserves its own article rather than being crowded in here.