Preheat the oven to 180°C. Line a large baking tray with baking paper.
Place the macadamias in the bowl of a food processor and process to coarse crumbs. Pulse the machine to get the nuts as fine as possible without creating a paste. Place in a bowl with 3 of the egg yolks, caster sugar, cardamom and rosewater and stir thoroughly to combine.
Roll teaspoonfuls of mixture into small balls and place on the prepared tray, 4cm apart. Repeat with remaining mixture.
Whisk the remaining egg yolk with 1 tablespoon of water and brush each cookie with a little of this mixture. Place a whole macadamia in the middle of each cookie and bake for 15 minutes, until golden.
Remove from the oven and allow to cool on the tray for 10-15 minutes before transferring to a wire rack to cool completely. Store in an airtight container.