Platinum Blondies

Name: Platinum Blondies
Ingredients: 2 sticks (16 tablespoons) unsalted butter, melted and cooled slightly, plus more for greasing; 2 cups all-purpose flour; 1 teaspoon baking powder; 1/4 teaspoon fine sea salt; 2 large eggs; 3/4 cup firmly packed dark brown sugar; 3/4 cup granulated sugar; 1 1/2 teaspoons vanilla extract; 2 cups (one 11-ounce bag) white chocolate chips, such as Ghirardelli; 8 ounces roasted, salted macadamia nuts, coarsely chopped (keep them bigger than the chips); 1 cup unsweetened coconut flakes