Brown the butter in a small saucepan on medium low heat, about 4-6 minutes. Transfer the brown butter to the stand mixer bowl and allow to cool completely.
In the meantime, finely chop the roasted macadamia nuts either by hand or in a food processor.
Sift the flour and cornstarch into a small mixing bowl. Stir in the kosher salt and finely chopped macadamia nuts. Set aside.
Once the brown butter has cooled completely, add the coconut milk, honey, vanilla extract and instant espresso powder. Beat with the paddle attachment until combined.
Add the flour mixture and stir until incorporated. Use a spatula to scrape the side and bottom of the bowl to ensure thorough mixing. Refrigerate the dough for at least 1 hour.
Divide the cookie dough with a small cookie scoop and roll into 1” balls, about 15 g each. This recipe will yield about 25 cookies.
Keep the cookie dough balls refrigerated while the oven is preheated to 350°F.
Place the dough balls on a cookie sheet about 1” apart and bake for 10 - 11 mins until the bottom edges are golden brown.
Remove the baking sheet from the oven and set it on a wire rack to cool for at least 10 - 15 minutes. When the cookies are cool enough to handle with your bare hand, roll them in powdered sugar and set them on another wire rack to cool completely.