Dress up our Classic Shortbread with coconut and macadamia nuts for a tropical taste. It's a sweet, nutty, and absolutely delightful dessert.
Preheat oven to 300 degrees, with rack in upper third. Sift flour and salt into a bowl; set aside. Put butter into the bowl of an electric mixer fitted with the paddle attachment. Mix on medium-high speed until fluffy, 3 to 5 minutes, scraping down sides of bowl. Gradually add sugar; beat until pale and fluffy, about 2 minutes. Beat in vanilla. Add coconut and macadamia nuts; mix to combine.
Reduce speed to low. Add flour mixture all at once; mix until just combined.
Butter an 11 1/2- by-8 1/2-inch rimmed baking sheet, and line with parchment, allowing a 2-inch overhang on long sides; butter parchment. Using plastic wrap, press dough into prepared pan. Leave plastic on dough, and refrigerate 20 minutes. Cut into 32 rectangles (about 3 by 1 inch each); prick top all over with a wooden skewer. Refrigerate 15 minutes.
Bake until golden brown and firm in center, about 40 minutes. Lift out by overhang; transfer to a wire rack to cool. Recut into rectangles.