1.Cut each cube in half, and spread one surface with jam and cream. Sandwich together.
2.Sift icing sugar and cocoa together into a large heatproof bowl. Stir in milk and butter.
3.Place icing over a saucepan of gently simmering water and heat gently, stirring, until icing sugar dissolves and mixture is smooth and runny (of coating consistency).
4.Using a fork, dip each cake piece into chocolate icing, draining off excess. Roll in coconut to coat. Place on a wire rack and leave to set. Store in an airtight container.
To prevent icing from becoming too thick, keep it over a bowl of warm water. Prepared sponge cake can be used instead of the Madeira cake. Alternatively, you can use your favourite buttercake recipe it is best made the day before making the lamingtons.