Alfajores With Coconut Dulce de Leche

Place a rack in middle of oven; preheat to 375°F. Bring condensed milk, coconut milk, and ½ tsp. salt to a boil in a small saucepan over medium-high heat. Scrape mixture into a 13x9" baking dish and bake, stirring every 15 minutes or so, until very thick and a light caramel color, 40–50 minutes. Mixture will look lumpy, broken, and very pasty—that’s exactly what you want. Let cool in dish 1 hour, then transfer to a food processor and process until smooth. Set dulce de leche aside for serving.

Meanwhile, whisk almond flour and 2¼ cups all-purpose flour in a medium bowl to combine. Using an electric mixer on medium-high speed, beat butter, sugar, and 1½ tsp. salt in a large bowl, scraping down sides and bottom of bowl as needed, until pale and creamy, about 3 minutes. Add egg yolk, vanilla, and ¼ cup honey and beat until combined, about 2 minutes. Reduce speed to low, add dry ingredients, and mix, scraping down sides and bottom of bowl, until incorporated. Divide dough in half and pat each piece into a 1"-thick disk. Wrap in plastic and chill until firm, at least 2 hours.

Preheat oven to 350°F. Roll out 1 disk of dough on a lightly floured sheet of parchment paper, dusting with more flour as needed to keep dough from sticking, to about ⅛" thick. Punch out shapes with lightly floured cookie cutters and transfer to 2 parchment-lined baking sheets, spacing 1" apart. Pat scraps into a 1"-thick disk, wrap with plastic, and chill 10 minutes if soft.

Bake a sheet of cookies, rotating halfway through, until edges are lightly browned, 7–9 minutes. Let cool 10 minutes on baking sheet, then transfer to a wire rack and let cool completely. Bake remaining sheet of cookies. Line baking sheets with fresh sheets of parchment paper and repeat process with remaining disk of dough.

Divide coconut evenly among 3 bowls. Add 1 Tbsp. food-coloring powder (sift if needed) to a bowl of coconut and toss until coconut is coated; add more powder if a more intense color is desired. Repeat with remaining food-coloring powder and another bowl of coconut. Leave 1 bowl of coconut white. If using, add some luster dust to all 3 bowls and toss to combine.

Turn half of the cookies over to expose flat side; spread 1 tsp. dulce de leche over (this will be the inside of the sandwiches); set aside.

Heat remaining 2 Tbsp. honey in a small bowl in the microwave just until warm (you want it to be loose), then stir in 2 tsp. warm water. Working one at a time, lightly brush honey over the top of remaining cookies (the ones that have not been filled with dulce de leche). Immediately dip tops into a bowl of coconut; press additional coconut onto cookie to cover any bald spots. Close up cookie sandwiches, coconut side up.

Do Ahead: Dulce de leche can be made 1 month ahead; place in an airtight container and freeze. Thaw in refrigerator overnight before using. Dough can be made 3 days ahead; keep chilled. Cookies can be baked (but not assembled) 2 days ahead; store airtight at room temperature.