Caramel shortbread, also known as Caramel shortcake, Caramel squares, Caramel slice, Millionaires' shortbread, and Millionaires' slice, is a biscuit confectionery item composed of a rectangular shortbread biscuit base topped with a very soft caramel filling and a milk chocolate topping.It is known at least since recipes and references in Australian journals and cookbooks from the 1970s, most notably in the The Australian Women's Weekly.