Soften the butter slightly in the microwave for about 20 seconds.
In the bowl of a standup mixer, add the butter, sugar, egg, and egg yolk, and cream together on medium-high speed for 2 minutes.
Add the all-purpose flour, baking powder, baking soda, and salt on top of the wet ingredients, and mix to combine on medium speed.
Add the vanilla and mix to combine.
Add the macadamia nuts and the optional white chocolate chips, and mix to combine.
Transfer the cookie dough to a Ziplock back and chill in the refrigerator for at least 1 hour (overnight is fine too.
Preheat the oven to 350F and line a cookie sheet with parchment paper.
Remove the cookie dough from the Ziplock back and, using your hands or a cookie scoop, form the dough into balls. The balls should be roughly 2-2.5 inches in diameter.
Place the dough balls on a cookie sheet lined with parchment paper 2-3 inches apart and bake for 12 minutes or until just barely golden around the edges.
Halfway through baking, remove the cookies from the oven and whack them on the counter. You will see them flatten and crack for a more visually appealing cookie.
Notes
Store leftover cookies in an airtight container at room temperature for 3 days, in the fridge for 1 week, or in the freezer for 6 months.
Leftover dough can be stored in an airtight container in the freezer for up to 6 months.