Preheat oven to 350 degrees F.
Lightly grease a 13 x 9-inch baking pan, or line with parchment paper.
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 prepapred pan and press 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.
While the cookie layer is baking, toast the coconut by placing in an even layer in a skillet on the stove over medium-high heat. Stir constantly until golden color is achieve. Transfer coconut to a plate and spread out to cool.
Once the cookie base has cooled, make the topping by placing the unwrapped caramels 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, cut into 30 bars with a large knife, a pizza cutter, or a pizza chopper.
Once bars are cut, melt 10 ounces of the chocolate in a small bowl by heating on high in the microwave in 45 second intervals, stirring thoroughly to prevent scorching. Dip the bottom of each bar into the chocolate and place on a clean piece of parchment or wax paper.
Melt the remaining 2 ounces of chocolate and transfer into a piping bag or a sandwich/storage bag with the corner snipped off and drizzle bars with chocolate to finish. Let chocolate set completely before storing in an airtight container. These bars also freeze well.
Note: For an easier finish, you can simply drizzle chocolate on top of the bars before slicing rather than dipping the bottoms. You will only need 2 ounces of chocolate for the drizzle, and you will not exactly get the Samoas look, but the results will still be delicious.