The oggie is a sandwich that builds its own container, and the name is the Cornish and Welsh word for the sealed baked pocket the rest of the country calls a pasty. Instead of putting a filling between slices, the pastry is rolled, loaded, folded over, and crimped shut, then baked sealed around the cargo, so the bread is engineered to the filling rather than the filling fitted to the bread. The crimp running along one edge is the defining feature: it is the seam and the handle at once, the part a miner gripped with dirty hands and discarded, and a weak crimp leaks its filling out under heat and the whole thing fails on the walk to wherever it is eaten.
The craft is in the pastry and the closure. The dough has to be strong enough to hold a wet, raw filling through a long bake without splitting at the seam, and sturdy enough to survive a coat pocket or a tin tucked into a bag down a shaft. The classic load is beef with potato, swede, and onion, sealed in raw so it part-steams inside its own crust while the pastry sets, which is why the bake time is set by the crust and not the centre. There is no separate sauce because the juice the vegetables and meat release is held inside the sealed pocket and becomes the sauce. It was built as a complete hot meal that lasted a working shift in the hand, and the engineering still reads that way: portable, self-contained, sturdy on purpose.
The variations are mostly regional and a question of what fills the pocket. The Cornish version seals the classic beef and root vegetables behind a rope crimp along the side; the Welsh oggie tends toward lamb with leek or vegetables and a crimp over the top. A sweet end, jam or apple sealed at one corner, turns it into a two-course pocket in a single piece, the same instinct as the Bedfordshire clanger. The vegetable and cheese-and-onion builds keep the sealed-and-baked logic with no meat at all. Each deserves its own article rather than being crowded in here.