Whizz the remaining macadamia nuts in a food processor until they are ground but still have a bit of texture.
Whisk the egg whites with a pinch of salt until they hold stiff peaks, gradually add 150g caster sugar and continue until you have a firm and glossy meringue.
Fold the ground nuts in gently with a large metal spoon or a spatula. Dollop a spoonful of meringue onto each of the circles on the baking sheets and spread out carefully to fill.
Bake for 45 minutes until dried out. Cool completely then gently release them from the paper.