With its layers of shortbread, caramel, and dark chocolate, Millionaire Shortbread is the candy bar of bar cookies. Each bite delivers a perfect blend of flavor and texture: sweet, salty, crunchy, and creamy. While Millionaire Shortbread looks fancy on a cookie plate, it is easier to make than you might think. The only special tool you will need is a candy thermometer to make the homemade caramel. Be patient during this step and make sure the caramel mixture registers between 236°F and 239°F. To make sure the bars can be lifted out of the baking pan easily, be sure to line the pan with aluminum foil, allowing 2 to 3 inches of foil to extend over the sides. Lightly grease the foil with cooking spray before pressing the shortbread mixture in the bottom of the pan. Slice the cookies into strips or small squares—like a millionaire, they are very rich.