Begin by preheating your oven to 350°F (175°C) and prepare a 9x9-inch baking pan by lining it with parchment paper or foil for easy removal.

In a mixing bowl, beat the room-temperature butter until smooth and creamy. Gradually add the sugar and salt, continuing to beat until the mixture is light and fluffy. Incorporate the egg yolk and vanilla extract, mixing well until combined. Slowly add the flour in portions, blending just until the dough comes together.

Press the dough evenly into your prepared baking pan, smoothing it out to the edges. Bake for approximately 22 minutes, or until the edges turn a light golden brown.

While the shortbread crust is baking, start preparing the caramel. It’s helpful to use a candy thermometer, though not absolutely necessary. Combine the butter, brown sugar, sweetened condensed milk, vanilla extract, salt, and either golden syrup or corn syrup in a medium saucepan.

Heat the mixture over medium heat, whisking continuously as everything melts and blends together. Allow the caramel to bubble gently, darkening in color. When it reaches around 225°F, or after about 5-6 minutes, it will thicken and begin to pull away from the sides of the pan. Your caramel is now ready.

Carefully pour the caramel over the baked shortbread crust, spreading it out evenly to create a smooth layer. Place the pan in the refrigerator for about 10 minutes to let the caramel firm up.

For the chocolate ganache, chop the chocolate chips and melt them with the heavy cream, either using a double boiler or by microwaving in short intervals (about 20 seconds each time), stirring between each burst. Once fully melted and smooth, pour the ganache over the caramel layer, spreading it evenly.

If you like, sprinkle a pinch of sea salt over the top for a finishing touch. Place the dessert back into the refrigerator to set before cutting into squares and serving.