In a medium mixing bowl, whisk together 350g (2 1/2 cups) gluten-free flour blend, 7g (1 teaspoon) baking soda, and 7g (1 teaspoon) salt. Set aside.
In a large mixing bowl, add 170g (3/4 cup) softened butter, 200g (1 cup) brown sugar, and 100g (1/2 cup) granulated sugar.
Cream with an electric mixer for 2-3 minutes, until light and fluffy, scraping down the sides of the bowl as needed.
Add 100g (2 large) eggs and 1 tablespoon vanilla extract and mix until smooth.
Add half of the flour mixture to the butter mixture and stir until just combined. Repeat with the remaining flour, stirring until no more streaks of flour remain.
Reserve about 2 tablespoons each of the chopped white chocolate and macadamia nuts for topping. Stir the rest into the dough.
Cover and chill the dough for at least one hour.
Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper.
Scoop the dough into 2-3 tablespoon balls. You should get about 24 cookies using a #24 scoop (2.7 tablespoons) and 18 cookies using a #20 scoop (3 tablespoons).
Place the cookie dough balls on the prepared baking sheet, leaving 3-4 inches between each one. You can fit 6-8 cookies per sheet. Keep remaining dough in the refrigerator until ready to bake.
Top the cookie dough balls with the reserved white chocolate and macadamia nuts before baking, after baking, or both.
Bake at 350°F (175°C) for 8-11 minutes, until the edges are lightly browned and the middle is no longer raw. The cookies will continue to bake on the sheet pan, so do not over-bake them for chewy centers.
While the cookies are still warm, use a round cookie cutter or biscuit cutter slightly larger than the cookie to scoot them into a perfect round shape.
Sprinkle with 1/2 teaspoon flaky sea salt immediately after removing from the oven. Let cool on the baking sheet for 4-5 minutes before transferring to a cooling rack.