Presoak your largest unglazed clay pot, top and bottom, in water for 15 minutes.
Place the prepared lamb in the pot, sprinkle with the nutmeg, then insert a meat thermometer in the lamb, away from the bone. Add all the remaining ingredients, except the arrowroot.
Place the covered pot in a cold oven.
Set the temperature at 480 degrees.
Cook for 2 hours, and then