Preheat the oven to 350 degrees F. Line a 9-inch square baking pan with aluminum foil, leaving about a 2-inch overhang on 2 sides. Spread the coconut in a single layer on a baking sheet and set aside.
Beat the butter, vanilla and salt with an electric mixer on medium speed in a large bowl until smooth and creamy. Add the confectioners' sugar and mix on low until just incorporated. Beat in the flour in 2 batches to make a smooth dough.
Lightly flour your hands and press the dough into the prepared baking pan. Bake the shortbread until the edges are firm and the top is dry, 28 to 30 minutes. Top the shortbread with the caramels in an even layer. Return to the oven along with the baking sheet of coconut and cook, tossing the coconut once, until the caramels are melted and the coconut is golden, about 10 minutes.
Spray the back of a spoon with cooking spray and use it to spread the caramel all over the shortbread. Sprinkle with the chocolate and let sit until the chips are melted, about 5 minutes. Sprinkle with the toasted coconut and let cool completely, about 1 hour.
Using the foil overhang as handles, lift the shortbread out of the pan and cut into 12 pieces.
When measuring flour, we spoon it into a dry measuring cup and level off the excess. (Scooping directly from the bag compacts the flour, resulting in dry baked goods.)
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