Brown meat and onions. Drain fat. Add mushrooms, cooked rice, sour cream, sherry (if ... I usually decrease ground beef to 1 pound, decrease sour ... may also be used.
Pour water over rice and let stand for 15 ... overnight. Bring casserole to room temperature and bake at 325 degrees for 1 - 1 1/2 hours. Serves 10-12.