Make Shortbread

1. Preheat oven to 325º
2. In a stand mixer with a paddle attachment, cream together butter and sugar for 1-2 minutes, starting on low speed and increasing to medium-high
3. When butter is almost creamed, and pale yellow in color, stop the mixer, scrape down the sides of the bowl and add the salt. Cream on medium-high speed for 60-90 seconds longer
4. Scrape down the bowl once again, and add the flour all at once. Start the mixer on low, and mix until the dough just comes together
5. Distribute pieces of dough evenly on parchment-lined sheet pan. Using a rolling pin or the palms of your hands, flatten dough evenly to fill the pan
6. Dock the dough with a skewer, fork, or dough docker evenly
7. Bake on the middle rack of the oven for 45 minutes, or until lightly browned, Remove the sheet pan to a cooling rack and allow to cool completely

Make Caramel

1. Combine sugar, corn syrup and water in a medium saucepan. Heat over medium-high, stirring only until the sugar is dissolved. You may swirl the mixture occasionally, but do not stir after this point. Allow to boil until sugar reaches a medium-brown color
2. Meanwhile in a separate pot, heat the cream, butter and salt until just simmering and the butter has melted. Remove from heat, set aside and keep warm
3. When the sugar mixture has started to just turn color, reduce the heat. Once it reaches the medium-brown color of choice, remove from heat and slowly add the cream, stirring with a wooden spoon until the foaming dissipates
4. Using a candy thermometer, bring the caramel mixture back to between 245º - 250º (firm ball stage) over medium-high heat. This may take up to 25 minutes, but be sure to watch the thermometer carefully. Do not stir, but swirl the pot occasionally
5. Once at 245º - 250º, remove from heat and stir in vanilla extract
6. Pour caramel over the cooled shortbread. Set aside to cool completely, at least 2 hours

Temper Chocolate

1. Bring 2" of water to a simmer in a medium saucepan and rest a heatproof bowl atop (making sure that the bowl does not touch the water)
2. Turn off the heat under the water and add ⅔ of the chopped chocolate (8 oz), to the bowl, and stir until the chocolate is melted. The residual heat will be enough to melt the chocolate
3. Remove bowl from the pot and stir in the remaining chopped chocolate until melted. If needed, return back to pot of steaming water to finish melting any remaining chocolate
4. Pour chocolate over cooled caramel and shortbread. Spread with a rubber spatula to smooth and assure that all caramel is covered
5. Let chocolate set for 20 minutes, so that it is still pliable, but not yet hard

Slice & Plate

1. With a bench scraper or chef's knife, score into bars through the chocolate and caramel layers (if this is not done at this stage, the chocolate will get too hard and shatter when cutting)
2. Let sit at room temperature until the chocolate is fully set, at least 30 minutes
3. Run a chef's knife all of the way through the shortbread layer, remove from pan, and serve
4. Keep stored in an air-tight container at room temperature