Simmer the lamb ( cover with water) and add the chopped onions, salt and pepper to taste. Simmer for 1 to 11/2 hr. or until tender.
When cooked, remove the meat and keep warm. Add water, if necessary to make the stock equal to 6 cups.
Add the milk and bring to boil, add the rice and cook on a very low heat. Add salt and pepper if needed.
Serve the cooked rice in a large platter and put the melted butter over the rice. Add the cooked lamb on top of the rice.
Sprinkle with parsely.