Millionaire shortbread, also known as millionaire's shortbread, is a confection made with layers of a high-fat, unleavened sweetbread; caramelized, condensed milk; and chocolate. It gets its texture from large amounts of butter, while heated condensed milk gives a creamy caramel filling, and quality baking chocolate is the base for a soft, rich topping. Additional ingredients and occasional add-ins may be incorporated. The treat is prepared in stages, with the bread being baked first, followed by the caramel and chocolate. Millionaire shortbread evolved from earliest recipes in Elizabethan-era Scotland, its decadent toppings being added as recently as the 19th century.
Shortbread is a sweet, unleavened cookie made from flour, sugar, and butter. The oldest recipes call for three parts flour, two butter, and one sugar, though contemporary versions may split this with powdered sugar. The cookie is named for its crumbly texture caused by the high fat content. Unlike shortcake, a related cookie, this treat never calls for vegetable oil or leavening agents.
Caramel makes up the filling in millionaire shortbread. At its simplest, caramel is any sugar heated to a syrupy or taffy-like texture, depending on cooking temperature. It may be mixed with butter or milk for a creamy texture. Most often, millionaire shortbread calls for sweetened, condensed milk to be heated to a caramelized state, though canned or melted caramel sauce may be used instead. The filling has a creamy, thick texture after cooling.
The chocolate topping is most commonly made with melted bittersweet or semi-sweet baking squares. Butter is added to maintain the chocolate's creamy texture during cooling. The quality of baking chocolate ultimately affects the shortbread's taste. Squares with a shiny texture and higher cocoa content are typically deemed as higher quality.
Additional ingredients can be added to millionaire shortbread to give variety to the basic cookie. Cornmeal, rice flour, or oats are additions for texture, while butter is sometimes added to the caramel filling for extra richness. Peanut butter, various nuts, and raisins may also be mixed into the chocolate topping to increase the flavor profile.
The shortbread layer is prepared first, with the dry ingredients being sifted together, and the sugar and butter creamed and beaten in later. After baking, the slightly-cooled caramelized milk is layered onto the shortbread, followed by the melted chocolate and any toppings or add-ins. The sheet is cut into squares before chilling in the refrigerator for several hours.
Shortbread's origins lie in Elizabethan-era Scotland, when the food was first made using ground oats. Contemporary recipes most commonly use wheat flour, though a variety of other grain meals can be used. Candied orange peel and almonds were added for special occasions as far back as the 19th century, around the same time that contemporary baking chocolate and sweetened, condensed milk were introduced, eventually leading to millionaire shortbread.