Step 1

Preheat the oven to 180C/160C fan forced. Grease and line a 18 x 28cm slice pan with baking paper, allowing paper to overhang the 2 long sides.

Step 2

Place the flour, rolled oats, sugar, coconut and cocoa in a large bowl. Stir in the butter, milk and vanilla. Press mixture over the base of the prepared pan. Bake for 25-30 minutes or until browned and cooked through. Set aside in the pan to cool.

Step 3

For the icing, combine the icing sugar and cocoa powder in a large bowl. Place the butter in a heatproof bowl. Pour over 2 tbsp of the boiling water. Stir until smooth. Stir into the icing sugar mixture, adding the 1 tbs remaining boiling water if necessary, until icing is well combined and spreadable. Spread icing over the slice. Decorate with extra coconut. Set aside until icing sets. Trim edges and slice to serve.