Preheat oven to 350°F (175°C). Grease baking trays and line with parchment paper.

In a mixing bowl, beat the softened butter and granulated sugar together until light and fluffy.

Sift the all-purpose flour and cocoa powder into the butter mixture.

Stir in the lightly crushed cornflakes and toasted desiccated coconut until well combined.

Place level tablespoonfuls of batter about 1 inch apart on the prepared baking trays.

Bake for 12 minutes, or until firm and light golden brown.

Let the cookies cool on the baking trays for 5 minutes.

Transfer the cookies to a wire rack to cool completely.

To make the chocolate icing, sift the powdered sugar and cocoa powder into a small heatproof bowl.

Stir in the soft butter and enough water to make a stiff paste.

Place the bowl over a small saucepan of simmering water and stir until the icing is spreadable.

Quickly spread the warm chocolate icing over the cooled biscuits.