Soak the pistachios in warm water for several hours, then rub them in a dishcloth to remove their skins. With a small, sharp knife make several incisions all over the roast and insert the pistachios. Tie the roast. Heat the lard in a flameproof casserole or dutch oven and brown the roast all over. Add the reserved bones, all of the remaining ingredients except the butter, and 1/4 cup water. Bring to a boil. Reduce heat and simmer 1 hour, turning the meat over occasionally. Add more water, if necessary. To serve, cut the meat into pieces. Strain the cooking liquid into a saucepan and bring to a boil. Remove the pan from the heat and whisk in the butter, a little at a time, swirling the pan until it melts completely. Serve in a gravy boat. Serve with small buttered mushrooms tossed with butter and parsley.
