The New Zealand Railways Magazine, Volume 9, Issue 9 (December 1, 1934)
Ingredients.—Icing sugar 1lb., butter 2 ozs., milk (hot) 1 tablespoon, vanilla essence (if liked).
Method.—Melt the butter in the hot milk. Sift the icing sugar into a basin. Add the essence. Gradually add the milk and butter, beating the mixture well with a wooden spoon until it is the consistency of thick cream. Spread this evenly over the cake. Use a knife dipped in hot water to obtain a nice smooth surface. Decorate the cake as desired.