Lightly coat a 13 x 9-inch pan with cooking spray or butter. Line the pan with waxed paper or parchment paper and coat with cooking spray or butter. (Buttering the tray before adding the paper helps keep it from slipping around while you're pouring in the hot caramel mixture.)
In a large pot over high heat, bring milk, corn syrup, sugar, and butter to a boil, stirring until sugar has dissolved. Continue to cook over medium-high heat, stirring frequently, until mixture reaches 248oF (120oC), firm-ball stage on a candy thermometer, about 20 minutes.
Remove from heat and stir in vanilla and salt. Pour into prepared pan, and allow to cool.
Shortbread:
In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
In a large bowl, cream together butter and sugar with a mixer or a sturdy fork until light and fluffy. Slowly add dry ingredients to the butter mixture. Mix the milk and vanilla into the dough, using a low-speed on the mixer, or the fork.
Separate the dough into two halves and wrap each half tightly in plastic. Refrigerate until the dough is firm.
Topping:
While the dough is refrigerating, preheat your oven to 350F (180C). Toast the shredded coconut on a baking sheet for about 10-15 minutes, stirring frequently. Let cool while shaping and baking cookies.
Line two baking sheets with silicone liners or parchment sheets.
Prepare cookies:
Once the dough is firm, roll it out on lightly floured surface to a thickness of 3/8-inch to ¼-inch thick. Cut out with biscuit cutter or two differently sized round cutters.
Bake cookies one sheet at a time for 10-12 minutes, rotating the cookie sheet 180°, halfway through baking. Set cookie trays on cooling racks and allow to cool for about 6 minutes before taking cookies off of the trays. Transfer cookies to the cooling rack. Allow cookie sheets to cool completely before putting new cookies to be baked on them, placing raw dough on hot sheets melts the butter and makes the cookies spread.
Place caramel, milk and salt in a microwavable bowl and microwave on high power for 1 minute at a time, stirring after each minute, until nice and melty (3-4 minutes). Stir the toasted coconut into the caramel. Using a knife or an offset spatula generously spread the caramel mixture on top of your completely cooled cookies. You may reheat the caramel mixture as needed if it becomes too hard to work with.
Lay sheet of waxed paper on the counter. Roughly chop the chocolate and microwave on high power in 30-second bursts, stirring between each, until melted. Dip the bottoms of your coconut-topped cookies into the chocolate and place on waxed paper to cool. Once all the cookies have been chocolate dipped, place the rest of the chocolate in a small ziptop bag. Cut a small hole in one corner of the bag, and pipe the chocolate on top of each cookie.
You’ll probably have leftover caramel and coconut topping. Roll this mixture into small walnut-sized balls using your hands, and dip it in melted chocolate to make caramel-coconut bon-bons.
Store cookies and bon-bons in air-tight containers or eat immediately! ENJOY!