Step 1

Whisk together flour, baking powder, cardamom, and salt in a medium bowl; set aside. Combine butter and sugar in a stand mixer fitted with the paddle attachment; beat on medium speed until mixture is light and fluffy, about 5 minutes, stopping to scrape sides of bowl as needed. Add egg and vanilla; beat until well combined, about 2 minutes. With mixer running on low speed, gradually add flour mixture; continue beating until dry ingredients are incorporated and dough just starts to clump together, about 2 minutes, stopping to scrape sides of bowl as needed. Turn mixture out onto a clean work surface. Knead until dough just comes together. Divide dough in half; shape into 2 disks. Wrap each disk tightly in plastic wrap; chill at least 1 hour or up to 3 days.

Step 2

Preheat oven to 350°F. (If dough has chilled longer than 2 hours, let stand at room temperature until slightly softened, about 10 minutes.) Unwrap 1 dough disk, and roll between 2 sheets of parchment paper to about 1/4 inch thickness. Remove top parchment sheet. Using a 2-inch fluted round cookie cutter, cut 36 circles from dough, rerolling scraps as needed. Arrange dough circles at least 1/2 inch apart on 2 baking sheets lined with parchment paper. (Discard dough scraps.) Freeze dough circles until firm, about 10 minutes. Bake in preheated oven until tops are dry but cookies have not started to brown, 10 to 11 minutes. Let cookies cool on baking sheets 2 minutes; transfer to a wire rack, and let cool completely, about 15 minutes. Repeat process with remaining dough disk to make 72 cookies total.

Step 3

Place white chocolate in a small microwavable bowl; microwave on high until melted and smooth, about 1 minute and 30 seconds, stirring every 30 seconds. Transfer chocolate to a piping bag or a ziplock plastic bag with an 1/8-inch hole snipped in the corner. Drizzle 36 cookies with chocolate. If desired, decorate chocolate drizzle with gold leaf and edible flowers. Chill drizzled cookies until chocolate is set, 5 to 10 minutes.

Step 4

Preheat oven to 300°F. Spread powdered milk in a thin, even layer on a baking sheet lined with parchment paper. Bake in preheated oven until light golden brown, 12 to 16 minutes. Sift through a fine wire-mesh strainer. Combine sifted powdered milk and dulce de leche in a large nonstick skillet; cook over medium-low, stirring constantly using a rubber spatula, until well combined and no dry bits of milk powder remain, 3 to 4 minutes. Add ghee, milk, salt, and cinnamon; cook, stirring constantly, until mixture is shiny, well combined, and mostly smooth, 4 to 6 minutes. Remove from heat; let cool 5 minutes.

Step 5

Transfer filling to a piping bag or ziplock plastic bag with a 1/2-inch hole snipped in the corner. (If bag is too hot to hold, wrap in a dish towel.) Arrange the 36 undecorated cookies upside down on a clean work surface. Pipe about 2 teaspoons filling onto center of each cookie. Sandwich with decorated cookies; gently press to spread filling to edges. Let cool 15 minutes.