In a medium mixing bowl, whisk together flour, baking soda, baking powder and salt; set aside.

Over medium-low heat, melt butter in a saucepan. Allow to simmer until the butter begins to turn a warm amber color with a nutty aroma. Pour the butter (including the more browned pieces settled at the bottom) into a mixing bowl. Allow to cool to room temperature, around 15 minutes.

Once butter has cooled, add brown sugar and granulated white sugar to the bowl, mix using a hand mixer on medium speed until well incorporated ensuring to scrap down the sides. Add eggs and vanilla, and continue to mix until combined and mixture lighter in colour.

Add in prepared dry ingredients and mix until just combined. Fold in white chocolate chips and macadamia nuts, do not overmix the batter. Place dough in refrigerator for 30 minutes to cool.

Preheat oven to 350°F (177°C) and line a large baking sheet with parchment paper or a silicone mat; set aside.

Remove cookie batter from fridge, scoop about a heaping tablespoon of the cookie dough at a time and roll into balls (use a cookie scoop if you have one on hand, mine were approx. 50g each). Place about 2 inches apart on the prepared baking sheets and bake for 10 minutes until edges golden brown. The centers will still be soft for "soft and chewy cookies". For crispier cookies, bake for an additional 1-3 minutes.

Remove from oven, sprinkle lightly with flaky sea salt and allow to rest for a few minutes on baking sheet, then transfer to a wire rack to cool completely.