Step 1

Place a rack in middle of oven; preheat to 375°. 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.

Step 2

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.

Step 3

Preheat oven to 350°. 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.

Step 4

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.

Step 5

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.

Step 6

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.

Step 7

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.

Step 8

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.