Place butter into the bowl of an electric mixer. Beat until smooth, slowly adding the icing sugar and mixing in well.
Add the flours and baking powder gradually, until all incorporated. Fold in macadamias. Remove to a lightly floured surface and bring together with your hands. Roll out to ½ cm thickness and use various sized star shaped cutters to cut shapes and place onto lined oven trays. Refrigerate for at least 20 minutes.
Pre-heat oven to 170°C (150°C fan-forced). Place trays of shortbread into the oven and bake for 20 minutes, or until just golden underneath. Allow to cool for 5 minutes on trays before removing to a wire rack to cool completely.
Place chocolate into a heat proof bowl and microwave at 50% for 30 seconds. Stir and continue in 15 second bursts until all melted and smooth. Dip cooled shortbread star tips into chocolate, sprinkle with coconut and allow to set on a wire rack.
To assemble trees, you may need to reheat chocolate gently. Using larger stars as the base layer, place a dollop of chocolate in the centre and place another star on top, continue with another 6-7 stars, gradually finishing with the smallest sized star at the top. Repeat with remaining stars.