In an electric mixer, cream butter, white granulated sugar, and powdered sugar. Add vanilla and egg. Scrape down the sides of the bowl between each addition.
Add flour, cornstarch, baking soda, baking powder, and salt. Keep mixing until the dough pulls from the side of the bowl and forms a ball in the center.
Using a 1.5-tablespoon cookie scoop, add a mound of cookie dough to a baking sheet lined with parchment paper or a silicone baking mat.
Refrigerate the dough for 1 hour.
After 1 hour, preheat the oven to 400℉. Place the baking sheet directly into the oven from the fridge. Bake for 11-12 minutes, until the tops are set and the centers are slightly underdone. Let cool.
Caramel Coconut Topping
While the cookies chill, make the topping. Preheat the oven to 350℉.
Spread the coconut flakes on a baking sheet and bake for 5-10 minutes until golden brown, stirring often because coconut can cook quickly.
Melt caramel bits and heavy whipping cream in a bowl. Add caramel flakes and stir. If too stiff, add additional cream. Season with a dash of salt.
Chocolate Ganache
Heat semisweet chocolate and heavy whipping cream until melted.
Dip the bottom of each cookie in the chocolate. Let set. If needed, place it in the fridge to harden the chocolate.
Use a 1-tablespoon cookie scoop or a spoon to add a dollop of caramel coconut topping to each cookie.
Drizzle the remaining chocolate on the top of each cookie.