Preheat the Oven:
Preheat your oven to 350°F (175°C). Line a 9×13-inch baking dish with parchment paper, leaving an overhang for easy removal.

Make the Shortbread Base:
In a large bowl, beat together softened butter and sugar until light and fluffy. Gradually add flour and salt, mixing until a crumbly dough forms. Press the dough evenly into the prepared baking dish.

Bake the Shortbread:
Bake for 20-25 minutes or until the edges are golden. Let it cool while preparing the caramel layer.

Prepare the Caramel:
In a saucepan over medium heat, combine butter, brown sugar, sweetened condensed milk, corn syrup, and salt. Stir continuously until the mixture begins to boil. Reduce heat to low and simmer for 5-7 minutes until the caramel thickens and darkens slightly, stirring constantly to prevent burning. Remove from heat and stir in vanilla extract.

Add the Caramel Layer:
Pour the caramel over the cooled shortbread base, spreading evenly with a spatula. Let it set in the refrigerator for about 30 minutes or until firm.

Make the Chocolate Topping:
Melt the chocolate chips and oil together in a microwave-safe bowl in 30-second intervals, stirring in between until smooth. Alternatively, melt over a double boiler.

Add the Chocolate Layer:
Pour the melted chocolate over the caramel layer, spreading it evenly. Chill in the refrigerator for 30 minutes until the chocolate is set.

Slice and Serve:
Once fully set, use the parchment paper to lift the bars out of the pan. Cut into squares using a sharp knife (run the knife under hot water for clean cuts).