Make the cookie base:
Combine the flour and salt in a bowl.
In a separate bowl, beat the butter with an electric mixer until pale and fluffy.
Add the sugar and beat until combined.
Add the vanilla.
Add the flour mixture and mix until just combined.
Shape the dough into a ball and wrap in plastic wrap.
Refrigerate until firm, about 1 hour.
Roll the dough out on a floured surface to 1/4 inch-thick.
Use a bowl or plate to cut it into a large circle (make sure it will fit on your baking sheet!).
Transfer the circle to a sheet of parchment paper, then place on a baking sheet.
Slice a smaller circle out of the center to create a ring.
Prick the surface with a fork, then bake at 325F for 20 minutes, or until the edges are just starting to brown.
Cool completely on the baking sheet.
Evenly sprinkle the shredded coconut onto a baking sheet lined with parchment paper.
Bake at 350F for 10 minutes, until the coconut is toasted.
Spread about half of the melted chocolate onto the underside of the shortbread cookie, completely covering the base.
Transfer the cookie to the freezer or fridge for the chocolate to set, while you make the topping.
Place the soft caramels, milk and salt in a pot and set to medium heat.
Stir constantly until the caramel has completely melted.
Pour the caramel into a bowl with the toasted coconut, reserving about 1/3 cup of caramel.
Mix the coconut and caramel mixture together.
Spread the remaining caramel onto the non-chocolate side of the shortbread cookie.
Generously spoon the coconut caramel mixture on top.
Drizzle the remaining melted chocolate on top of the coconut.