Pre-heat oven to 350℉ and line your baking sheets with parchment paper.
Toast your macadamia nuts in a small baking dish for 5-10 minutes in the oven, until they start to brown. Watch carefully as they could burn easily. (Doing this is worth it and adds so much flavor) Remove from oven and let cool.
In a large bowl, cream together your butters and sugars until light and fluffy. Add your eggs and vanilla extract. Mix until well combined.
Add your flour, cornstarch, baking powder, baking soda and salt and mix until just combined.
Pour your toasted chopped macadamia nuts, and white chocolate chips into your cookie dough, saving some for the tops of the cookies.
Scoop your cookie dough out into 1-2 inch balls and place on your baking sheets lined with parchment paper a few inches apart. Top with extra toasted macadamia nuts and white chocolate chips.
Bake for 8-10 minutes until cookies start to get golden. Remove them from the oven and let cool. Top with flaky sea salt if desired.
Let cool, serve, share and enjoy!!