How to Make Millionaire's Shortbread, the Easy British Dessert That Tastes Incredibly Luxe

My colleagues know I have a big sweet tooth: I eat a lot of chocolate mousse, I make a mean icebox cake, and I can correctly identify Haagen-Dazs strawberry ice cream with my eyes closed. What they don’t know is that my love—or, perhaps more accurately, need—for sweets is so great that I turn into a Gremlin after 3 p.m. if I haven’t had my daily sugar fix. When I lived in Scotland, that was often a slice of cake or millionaire’s shortbread, a popular British confection of shortbread layered with caramel and chocolate. 

I no longer live in Britain, but I do still yearn for my afternoon slice of millionaire’s shortbread. Unfortunately, the treat is a little harder to come by in the U.S., and the ones I have eaten here are often disappointing and overly sweet, with stale, brittle biscuits and a chalky caramel that tastes like it's heavy on the corn syrup. I took it upon myself to create the best possible version: one with a tender, crumbly shortbread base and a deeply flavored, just-salty-enough butterscotch filling, along with a topping of dark chocolate that's bittersweet enough to prevent the dessert from being unbearably cloying.

In other words, the best millionaire's shortbread is luxe but tasteful, not gauche and gaudy—because the question isn't just who wants to be a millionaire, but what kind of millionaire do you want to be? The recipe here is my answer.

A Brief History of Millionaire's Shortbread

Many, including Felicity Cloake, a food writer for The Guardian, credit Australian Women’s Weekly with printing the first recipe for millionaire’s shortbread sometime in the 1970s, though not under that name. A quick peek at old cookbooks and newspapers, however, suggests the recipe is older than that. A recipe for shortbread caramel fingers in a 1965 edition of The Surrey Mirror and County Post instructs cooks to pour caramel—made from butter, caster sugar, syrup, and a small tin of condensed milk—over shortbread, letting it set, then topping it with half a bar of melted milk chocolate before slicing into fingers or squares. “Delicious and unusual,” the unnamed writer notes.

Today, the dessert goes by several names; I’ve seen it referred to as a caramel square, caramel slice, or caramel shortbread. In Scotland, it’s commonly referred to as millionaire’s shortbread, though it’s unclear exactly why or when the name became attached to it. Luckily, you don’t have to be a millionaire to make or enjoy it— you might, however, feel like you’ve won the lottery after tasting it.

5 Tips for Making the Best Millionaire's Shortbread

Start with good shortbread. You can’t go wrong with shortbread, caramel, and chocolate, but for a truly superb bar, each component should be good enough to enjoy on its own. The shortbread base in the recipe below is a slightly different version of one I’ve published before. The original shortbread recipe comes from Gaga, my husband’s grandma; here, I’ve slightly tweaked it so the cookies are made with all-purpose flour (instead of a combination of all-purpose and whole wheat flour), which more closely mimics the flavor and texture of the base used in traditional millionaire’s shortbread. 

Unlike many traditional shortbread recipes, which have you cream softened butter and sugar together, Gaga’s simple one-bowl method has you pour melted butter over the flour, cornstarch, sugar, and salt. Though I’ve changed her recipe slightly here, the method—and why it works—is still the same. The melted butter evenly coats the dry ingredients, which minimizes gluten development and produces a rich, tender shortbread. There’s also a significant amount of rice flour or cornstarch, which dilutes the gluten proteins in the all-purpose flour and reduces the overall gluten in the dough. (You can read more about it here.)

Cook the butterscotch to the right temperature. Cook caramel for too long, and you end up with a tough, brittle candy. Cook it too short, and you have a runny sauce. To ensure you have the right texture—soft but satisfyingly chewy—it’s essential to cook the butterscotch to the right stage, and the most accurate way to do that is to take the temperature. 

In my recipe below, I have you take the butterscotch to 235ºF (113ºC). This is the lower end of what pastry chefs refer to as the soft-ball stage, which ranges from 235 to 239ºF (113 to 115ºC), one of several stages used to describe the water content of sugar syrups. “The higher the temperature the syrup has reached, the less water remains in the sugar, and the firmer the resulting samples of sugar will be,” writes pastry chef Peter Grewling in the Culinary Institute of America textbook Chocolate and Confections. 

At the soft-ball stage, a drop of the syrup into a glass of cool water forms a malleable or soft ball. Praline or caramel candies taken to the soft-ball stage are often firm but pliable, and have a pleasant chewiness. In my testing, I found 235ºF (113ºC) to be the sweet spot. You can experiment with temperatures to find a texture that suits you best, but I don’t recommend exceeding 239ºF (115ºC), as the butterscotch may become too hard to enjoyably eat.

Skip the condensed milk. Many recipes for millionaire’s shortbread call for cooking condensed milk with butter, sugar, and occasionally corn syrup or golden syrup to form the caramel. In my testing, I found that condensed milk caramels weren’t easier, faster, or more delicious than a caramel or butterscotch filling made from scratch. (A note on terminology: Caramel is technically made from granulated sugar, while butterscotch is made with brown sugar. Recipes for millionaire's shortbread tend to refer to the middle layer as a "caramel," but if the filling is made with brown sugar—which is typically the case, if a recipe doesn’t call for condensed milk—then it’s butterscotch.)

To make the bar’s filling, I call on several pantry and fridge staples—unsalted butter, dark brown sugar, heavy cream, and salt—which I simmer on the stove until it reaches the soft-ball stage. The dark brown sugar brings a deep molasses and toffee note, resulting in a more flavorful butterscotch filling, while the cream and butter add richness.

Chill the bars in stages. After you pour the butterscotch filling over the shortbread, it’s essential to chill the bars before adding the chocolate layer. I let it cool first at room temperature, then transfer it to the fridge to further set. A quick stop in the freezer while I whip up the chocolate topping is just enough to get it firm enough to slice neatly while also helping the chocolate set a little faster once poured on top.

Top it with dark chocolate. The biggest risk with a dessert like this is that it can come out cloyingly sweet—that is, after all, what can happen when you take a cookie and top it with caramel and chocolate. But that doesn't mean a more balanced result isn't possible, it just requires attention to the details. One of the easiest ways to ensure the millionaire's shortbread isn't unbearably sweet is by choosing the chocolate wisely. 

I recommend topping the bars with dark chocolate that's around 64 to 72% cacao, as its bittersweet flavor helps offset the intense sweetness of the butterscotch and shortbread. Though you’re more than welcome to use milk or white chocolate, the bars will be much, much sweeter, and there’s nothing to keep you from spiraling into utterly saccharine territory.

Don’t forget the salt. There's hardly a dessert out there that doesn't benefit from the addition of salt, but it's especially important here. Once again, it’s all about balancing out the inherent sweetness of the components, and a judicious use of salt in each layer goes a long way towards that. From the shortbread to the butterscotch and the chocolate topping, a noticeable pop of salt  counters the sugar and keeps one foot in beautifully salty-sweet, ever so slightly savory territory.