Preheat your oven to 180°C (350°F). Line a square baking dish (about 8 x 8 inches) with parchment paper, leaving some overhang for easy removal later.

In a mixing bowl, cream together the softened butter and granulated sugar until light and fluffy, about 3-4 minutes with an electric mixer on medium speed.

Gradually fold in the flour and salt until the mixture comes together into a dough.

Press the shortbread mixture evenly into the prepared baking dish, smoothing the top with the back of a spoon.

Bake the shortbread for 20-25 minutes or until lightly golden. Remove from the oven and let cool completely.

In a saucepan over medium heat, combine the light brown sugar, sweetened condensed milk, and Biscoff spread. Stir until smooth and the mixture begins to bubble, cooking for about 5 minutes, stirring constantly.

Pour the caramel mixture over the cooled shortbread base, spreading it evenly with a spatula. Let it set for at least 30 minutes.

Melt the dark chocolate in a microwave or double boiler until smooth. Pour it over the caramel layer, spreading it out evenly.

Sprinkle sea salt flakes on top for an added flavor punch.

Chill the entire dessert in the refrigerator for at least 2 hours or until the chocolate is firm.

Once set, lift the dessert out of the pan using the parchment overhang, cut into squares, and serve.