Preheat oven to 160 degrees celsius (fan-forced). Grease and line with baking paper a 20x20cm square tin.
Place butter into the TM bowl and melt for 3 minutes, 100 degrees, Speed 1. Leave to cool.
Add the sugar, egg and vanilla to the TM bowl and mix on Speed 5 for 20 seconds. Scrape down the sides of the bowl.
Sift flour and cocoa into the bowl and add ½ cup coconut. Mix on Speed 2 for 20 seconds or until mixture has combined (use the spatula to assist with mixing).
Spread mixture evenly into pan.Bake for 25-30 minutes or until just firm.
To make the icing, place the icing sugar and cocoa powder into the TM bowl and press Turbo 5 times to sift.
Add butter and boiling water. Mix together on Speed 5 for 15 seconds or until smooth (add a little more water if the icing is too thick).
Spread warm slice with icing.Sprinkle remaining 2 tbs coconut over slice.