Slumpie, in context, would appear to be one of those filling dishes devised by a social group only a few pennies away from utter poverty, and who have therefore devised a tasty and effective means of making every penny feed a dollar's worth of mouths. The cheapest possible cut of mutton is left to disintegrate into a stock for at least six hours, taking with it as many of the cheapest forms of bulk vegetables (potatoes, swede, cabbage) as may be added to the pot. When the last shred of meat has fallen off the bone, the bone is removed (but not thrown away) and the slumpie is ready to serve. More affluent diners might consider making dumplings from suet fat, breadcrumbs and flour, and lobbing these into the gravy where they float like mines waiting for a battleship. The result is a dinner Enrico Basilica would give his right arm for, even before Nanny Ogg adds any extra flourishes to it.
Roundworld referents might be scouse in all its forms - a meat and veg stew, mutton-based, that gives a proud name to a proud people. Inland, it is called Lancashire hot-pot, and generally served under a roof of sliced cooked potato. Lobscouse substitutes available cheap cuts of fish for the mutton, while Blind scouse is the Angua-friendly vegetarian version with no meat at all..