MAKE THE COOKIES:
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and sugar until light and fluffy.
In a separate bowl, whisk together the flour, baking powder, and salt. In three increments, add the flour mixture to the creamed butter, mixing between each addition and scraping down the sides of the bowl as necessary. Add the milk and vanilla extract, blending until combined and the dough begins to come together in large pieces.
Use your hands to divide the dough in half, pressing it together to compact it into two disks. Wrap the disks securely in plastic wrap and refrigerate them until firm, about 1 hour.
Preheat the oven to 350ºF.
Once the dough has chilled, roll each disk out onto a lightly floured surface until it is 1/8-inch thick. Cut out as many cookies as possible with a doughnut-shaped cookie cutter. Place the cut-out cookies on a Silpat or parchment paper-lined baking sheet and repeat with remaining dough.
Bake the cookies for 10 to 12 minutes, rotating the baking sheet halfway through, until the cookies are pale golden brown. Transfer the cookies to a wire rack to cool completely.
MAKE THE COCONUT TOPPING:
Spread the coconut flakes onto a baking sheet lined with parchment paper. Bake the coconut for about 10 minutes in a 350ºF oven until toasted, stirring frequently to ensure even browning and so that it does not burn.
Melt the caramels, milk, and salt in a double-boiler by placing the caramels in a medium saucepot set over a large saucepot of simmering water. Cook, stirring, until the caramels are fully melted.
Remove the saucepot from the heat and combine 3/4 of the caramel with the toasted coconut in a large bowl.
Carefully spread the remaining 1/4 cup of caramel atop the cooled cookies then press on a portion of the coconut mixture. Let the cookies cool for 30 minutes.
Melt the dark chocolate in a double-boiler or in the microwave. Dip the bottoms of the cookies in the chocolate and place them on a wax paper-lined baking sheet. Use a fork to drizzle the tops with chocolate. Let the cookies sit until the chocolate hardens fully.