Preheat oven to 185°C. In a bowl, take the butter, using an electric mixer, beat well. Then add sugar and a pinch of salt. Beat until pale and fluffy.

Add flour, cocoa powder and cornflakes, and stir to combine.

Roll tablespoonfuls of mixture into balls, flatten slightly and place on greased and lined baking trays, 2 cm apart. Bake for 15 to 20 minutes or until just firm.

Set aside to cool.

To make the icing, whisk icing sugar and cocoa powder together with 2 tbsp water until combined to a thick paste consistency.

Add more water, 1 tsp at a time, if necessary.

Immediately spread over cooled biscuits and top each with a little of the chopped walnuts, to decorate.