Preheat your oven to 350°F (175°C). Line your baking dish with parchment paper, ensuring it hangs over the edges for easy removal.

In a mixing bowl, cream together the softened unsalted butter, granulated sugar, light brown sugar, and salt until the mixture is airy and fluffy.

Gently mix in the large egg yolk and vanilla extract until fully incorporated.

Gradually add the all-purpose flour to the butter mixture, stirring until just combined. Press this dough into the prepared baking dish evenly and bake for 20-25 minutes until golden brown.

For the caramel layer, combine sweetened condensed milk, unsalted butter, light brown sugar, light corn syrup, and salt in a saucepan over medium heat. Whisk continuously until thickened.

Once the caramel has thickened, remove it from heat and stir in the vanilla extract.

Pour the thick caramel over the cooled shortbread base, spreading it evenly. Chill in the refrigerator until set, about 1-2 hours.

For the topping, melt the semisweet chocolate chips with the heavy whipping cream until smooth and pour over the set caramel layer.

Finish by sprinkling sea salt over the chocolate topping. Allow the entire dessert to chill until the chocolate is firm, around 1 hour.