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