Mix together the paprika, cumin, butter, and salt, and spread over the mutton.
Loosen some of the skin just under the shoulder and put a little of the mixture inside.
Cook in the oven with the fleshy part of the meat facing down. Add a glass of water. Baste with the juice from time to time so that the meat does not dry up.
After about 2 hours, turn the meat over and do the same with other side and cook until golden brown.
Leave for 30 minutes and remove when meat can be torn off with the fingers. Arrange on a dish without the gravy.