To prepar the Afghan biscuits start heating the oven to 180°C/160°C fan.
Put the butter and sugar into a bowl and beat together until light and creamy.
Sieve the flour and cocoa together and stir into the creamed mixture.
Add the cornflakes and walnuts and mix well.
Shape the mixture into balls and place on a greased baking tray.
Bake for about 15 minutes until firm.
Cool on a wire rack.
Put the chocolate, cream and butter into a bowl over a pan of hot but not boiling water.
Heat until melted.
Remove the bowl from the heat and stir until the mixture starts to thicken.
Spoon a little icing on top of each cookie. Leave the Afghan biscuits to set.