1. Preheat the oven to 375 degrees F. Grease a 9-inch square pan and set aside.

2. To prepare the shortbread crust, place the flour and brown sugar into a medium bowl. Cut in the butter with a pastry cutter or fork until the mixture is even, creating a texture similar to grains of sand. Form the dough into a ball.

3. Press dough into the pan and prick holes all over the top with a fork.

4. Bake the crust for 20 minutes or until golden brown. Remove from the oven and let cool in the pan.

5. While the dough cools, make the caramel. Combine the sweetened condensed milk, salted butter, brown sugar, and salt in a small saucepan over medium-low heat. Cook, stirring constantly, until the caramel begins to boil. Reduce heat to low and cook until golden and pulling away from the sides of the pan, 4 to 5 minutes.

6. Pour the caramel over the cooled crust and refrigerate until firm to the touch (about 1 hour).

7. While the caramel and shortbread are cooling, prepare the chocolate ganache. Heat the chocolate chips and heavy cream in a double boiler or 30 seconds at a time in the microwave. Stir frequently, until fully melted, combined, and smooth, about 5 minutes. Let cool for an additional 5 minutes.

8. Spread the melted chocolate over the caramel-shortbread, and sprinkle the flaky salt evenly on top. Refrigerate until chocolate hardens (about 15 minutes). Cut into bars and garnish with small pieces of gold leaf, if desired.