Whisk flour, baking soda, and salt. Line baking sheets with parchment and roughly chop macadamias into pieces smaller than a whole nut.
Beat butter and both sugars for 3 minutes until creamy. Add egg, extra yolk, and vanilla; scrape the bowl and mix until smooth.
Mix in the dry ingredients briefly. Fold in white chocolate chips and macadamias, taking care to distribute the nuts evenly.
Cover and chill for 45 minutes. Heat the oven to 350°F (175°C) as the dough becomes firm enough to scoop.
Divide into 24 portions and arrange 2 inches apart on a cool sheet. Keep the remaining dough chilled between batches.
Bake 10–13 minutes, until the edges are golden and the centers look set but soft. Watch exposed white chocolate for excessive browning.
Cool on the sheet for 5 minutes before transferring to a rack. Warm cookies may bend around larger nut pieces.
Allow to cool completely before storing. If making multiple batches, give the empty baking sheet time to return to room temperature.
