Reestit Mutton is a variation of the Scandinavian skerpikjøt, an air dried mutton, or vivda, Norse for 'leg meat'. It is a traditional Shetland way of preserving mutton with salt for consumption during the winter months. The mutton is first salted in brine and was then traditionally hung in the rafters (reest) of houses, where the peat smoke with add flavour and help preserve the meat. It could very likely be called Shetland's national dish.
The first time I'd ever tried reestit mutton soup was during the annual Up Helly Aa celebrations. It was running late into the night and there was a very busy group of women in the local hall I was at serving polystyrene cups full of piping hot reestit mutton soup and trays of salt beef bannocks to the revellers.
It was an absolutely fantastic cup of soup, I recall. The next time I was in my local butchers, the old Globe Butchers on Commercial Road, I made sure I picked up a copy of their reestit mutton soup recipe.