I had that old paperback cookbook for years, and recently got rid of it in a downsizing move, but now sadly regret not taking out that one recipe for the orange coconut cake. It was absolutely delicious. The one I had was already old, as it belonged to my mother, and I am 66 years old. But it was the only cookbook she owned, as not many were made in those days. But the reason your mother-in-law probably remembers the coconut in the icing is because the really unusual touch was that after you iced the cake, you covered it with coconut that you had rubbed with fresh orange zest, so the coconut took on an orange color, and flavor, and was absolutely delicious! I am sorry I don't have the recipe to pass on to you, but I came on the net specifically trying to locate it, so if I find it, I will post it. Best regards, Lorna M.