Preheat oven: Adjust an oven rack to the center of the oven and heat to 320°F (160°C). Prepare a cookies sheet or line a baking tray with parchment paper while you wait.
Mix: butter, brown sugar, superfine sugar, egg, and vanilla extract in a large mixing bowl, and whisk well until combined.
Using a sieve: Sift in self-raising and all-purpose flour with baking powder, then stir through with a spatula.
Nuts and chocolate: Add crushed macadamia nuts and white chocolate chips, and continue to mix until combined without over-mixing. The dough should be slightly soft and sticky with some dry crumbs.
Scoop and roll: each cookie dough into a ball. Then slightly flatten each ball and place it onto a cookies sheet or baking tray, leaving space between them.
Bake: In a pre-heated oven, bake one tray at a time for 12-14 minutes.
Rest: Leave the cookies on the baking tray for 5 minutes to cool down slightly before removing them onto a cooling rack.