**Preheat the Oven:** Set to 350°F. Line two baking sheets with parchment paper.
**Mix Dry Ingredients:** In a small bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
**Cream Butter and Sugars:** In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar with an electric hand mixer on high speed until fluffy, about 3 minutes. (If using a stand mixer, use the paddle attachment.)
**Add Wet Ingredients:** Add the egg yolks and vanilla to the butter mixture. Mix on high speed until pale and fluffy, about 1-2 minutes.
**Combine Mixtures:** Gradually add the dry ingredients to the wet ingredients, mixing on low speed just until combined.
**Add Chips and Nuts:** Stir in the white chocolate chips and chopped macadamia nuts using a rubber spatula.
**Scoop Dough:** Use a 2-tablespoon cookie scoop to portion the dough into balls. Place them 2 inches apart on the prepared baking sheets.
**Bake:** Bake for 10-11 minutes. Let the cookies cool on the baking sheet for 5 minutes. If using, sprinkle with flaky sea salt.
*Optional:* To perfect the shape, use a large circular cookie cutter to swirl around each cookie while they are still hot, creating a perfect circle.
**Cool and Store:** Transfer the cookies to a wire rack to cool for 10-15 minutes, or until cool enough to handle. Store leftovers in an airtight container for up to three days, or freeze for up to two weeks.
Enjoy these delicious cookies with a glass of milk or your favorite beverage!