Mix stuffing mix, butter and 1 cup water. Put half stuffing mix in large greased pan. For second layer, combine cut up chicken, onion, mayonnaise and salt. Top with remaining stuffing mixture. Beat eggs and milk; pour over and refrigerate 4 hours or overnight. One hour before serving, top with chicken soup, mixed with one can water. Bake at 350° 50 minutes. Remove from oven and sprinkle with cheese. Bake an additional 10 minutes.