Preheat oven to 350 degrees. Line a 9 x13x 2-inch baking pan with parchment paper.
Cookie: In a large bowl, cream together sugar and butter, until fluffy. Beat in egg and vanilla extract. Working at a low speed, gradually beat in flour and salt until mixture is crumbly, like wet sand. The dough does not need to come together.
Pour crumbly dough into prepared pan and press with your hands into an even layer. Bake for 20-25 minutes, until base is set and edges are lightly browned. Cool completely on a wire rack before topping.
Topping: Preheat oven to 300. Spread coconut evenly on a baking sheet with sides, and toast 15-20 minutes, stirring every 5 minutes, until coconut is golden. Cool on baking sheet, stirring occasionally. Set aside.
Unwrap the caramels and place in a large microwave-safe bowl with milk and salt. Cook on high for 3-4 minutes, stopping to stir a few times to help the caramel melt. When smooth, fold in toasted coconut with a spatula.
Put dollops of the topping all over the shortbread base. Using the spatula, spread topping into an even layer. Let topping set until cooled.
When cooled, carefully remove from the pan and cut into 30 bars with a large knife or a pizza cutter (it’s easier to get it through the topping).
Once bars are cut, melt chocolate in a small bowl. Heat on high in the microwave in 45 second intervals, stirring thoroughly to prevent scorching.
Dip the base of each bar into the chocolate and place on a clean piece of parchment or wax paper. Transfer all remaining chocolate into a piping bag or a Ziploc bag with the corner snipped off and drizzle bars with chocolate to finish. (If you don't have enough chocolate left over, you may have to melt additional chocolate) Sprinkle with additional toasted coconut if desired.
Let chocolate set completely before storing in an airtight container.