Divide the macadamias evenly into 2 separate mixing bowls. To one, add the chilli powder, maple syrup, ¼ teaspoon of salt and 2 teaspoons of oil. Stir thoroughly to coat the macadamias with the mixture. To the second bowl of macadamias, stir through the rosemary, remaining salt and oil. Place all the macadamias, keeping the flavours separate, on a tray that can go on the BBQ - cast iron is ideal.
Preheat the BBQ to 250°C. Place a baking rack over the BBQ grill so that the tray will not come in direct contact with the grill (this will prevent them burning). Place the macadamia shells into a smoker box and close it. Place the smoker box into the BBQ and close the lid of the BBQ. Allow the macadamia shells to start smoking, about 15 minutes. Place the tray of macadamias into the BBQ and close the lid. Turn the BBQ down to about 150°C and let the macadamias cook slowly, stirring occasionally, for about 20 minutes. Turn the BBQ off and allow the macadamias to cool in the BBQ with the lid down for 20 minutes to increase the smoky flavour. Serve slightly warm or cool completely and store in an airtight container.