Lamb is widely accessible in the U.S., but ... However, because mutton is slaughtered when older, it will need a longer cooking time and a different cooking method to make it fork-tender.
It's difficult to carve, so either buy it boned and rolled, or else roast it slowly to allow the generous layers of fat to melt away, leaving tender meat that can be pulled off the bone in large ...
His spice mixture makes enough for two legs of lamb but it is worth making the entire amount, rather than halving the recipe; store the excess in an airtight container and freeze it for another ...