01 -
Preheat the oven to 350°F and line a 9x9 inch baking dish with parchment paper or aluminum foil.
02 -
Cream together butter, granulated sugar, and salt until light and fluffy. Add vanilla extract and egg yolk, then mix until combined. Gradually incorporate the flour, mixing until the dough just comes together.
03 -
Transfer the dough to the prepared pan and press into an even layer. Bake for about 22 minutes, or until the edges are golden brown. Remove from oven and set aside.
04 -
While the shortbread cools, combine butter, light brown sugar, salt, vanilla extract, sweetened condensed milk, and syrup in a saucepan over medium heat. Whisk continuously as the mixture melts and begins to bubble. Continue cooking, stirring often, until the caramel thickens, darkens in color, and reaches 225°F, about 5-6 minutes.
05 -
Carefully pour the hot caramel over the shortbread base, spreading evenly to the edges. Chill in the refrigerator for 10 minutes to allow the caramel to set.
06 -
Chop the chocolate and combine with heavy cream in a heatproof bowl. Gently melt using a double boiler or by microwaving in 20-second bursts, stirring between each interval, until smooth and glossy.
07 -
Pour the melted chocolate ganache over the chilled caramel layer. Smooth the surface evenly and sprinkle lightly with sea salt. Return to the refrigerator to set, then slice into bars for serving.