Why It Works
- Aside from the superlative flavor they bring, adding ground pistachios to the shortbread keeps the dough from developing gluten and becoming tough.
- Fruity, citrusy coriander adds welcome complexity to the whiskey-spiked butterscotch sauce.
- The acidity of dark chocolate offsets the sweet richness of the butterscotch and shortbread.
Millionaire's shortbread—the bar cookie of shortbread topped with layers of caramel and chocolate—is one of those "I can't believe we ate the whole thing" desserts. It's not to be taken lightly. But if you have the power to resist inhaling a batch of warm, gooey, caramel- and chocolate-slathered butter cookies, you're a stronger soul than I.
Sadly, millionaire's shortbread is one of those awesome things that often suffers from shortcuts. The shortbread, that oh-so-simple mix of butter, sugar, and flour, can turn out tough and greasy when not handled with care. The caramel? All too often it's a cheaty condensed milk concoction that lacks the complexity of scorched sugar. And the chocolate is frequently low quality and way too sweet.
Shortbread deserves more than shortcuts, which is why I love this recipe so much.
Let's start from the bottom with the shortbread. Half the dry mass of the dough is crushed pistachios, not flour, which makes for an especially workable dough that doesn't form enough gluten to turn tough. Oh, and the flavor's a big upgrade over standard shortbread—all the fruity, nutty complexity of pistachios with a kiss of lemon zest to lighten it up.
But the heart and soul of this cookie is the middle layer. It's not a caramel; it's butterscotch, made with raw sugar toasted in plenty of butter, then turned into sauce with cream, whiskey, and (the secret weapon) ground coriander, whose floral, musky, citrusy character does magical things with Scotch or Irish whiskey.
Then there's the chocolate: a dark, bittersweet chocolate with some acidity to cut through the sugar, topped with salt and more coriander before it has a chance to cool.
Some cookie snobs stigmatize bar cookies as somehow less impressive or delicious than round ones. Go ahead, make these for them and watch them try to turn up their noses.
You can serve this dessert in a couple ways. My favorite is to plate big slabs of warm-from-the-oven shortbread, then spoon on the toasty butterscotch and add a drizzle of melted chocolate. It should be eaten with a fork, ideally with tea. But you can also make bar cookies: let the shortbread cool completely, then spread on the butterscotch and pop it in the fridge till it's cooled into a semi-hard candy. Spread on the chocolate, chill again, and cut into squares (which freeze beautifully).
- For the Pistachio Lemon Shortbread
- 1 cup (2 sticks) unsalted butter, softened
- 3/4 cup sugar
- 1 1/2 teaspoons kosher salt
- Zest of one lemon
- 1 1/4 cups (8 ounces) shelled pistachio nuts
- 1 1/2 cups all-purpose flour
- For the Coriander Butterscotch
- 1/2 cup (1 stick) unsalted butter
- 1 1/2 cups raw (turbinado) sugar
- 1/2 cup heavy cream
- 1/2 cup Irish whiskey
- 2 tablespoons coriander, toasted and freshly ground, plus more for dusting
- 2 teaspoons kosher salt
- For the Chocolate Topping
- 8 ounces dark chocolate, about 70% cacao, chopped fine
- 2 tablespoons unsalted butter
For the Pistachio Lemon Shortbread: Preheat oven to 350°F (180°C). In a stand mixer fitted with the paddle attachment, cream butter, sugar, salt, and lemon zest on high until pale, fluffy, and almost smooth. Scrape down sides of bowl with a rubber spatula as needed.
In a food processor, crush pistachios to a fine meal. Small chunks are fine. Decrease mixer speed to medium and add pistachios. Turn mixer down to low and add flour in half-cup installments, scraping down bowl as needed. When all flour is incorporated, increase speed to high and mix just until dough comes together in large clumps.
Turn dough out onto a sheet pan and press down with hands to a 1/2-inch rectangle, approximately 12 inches by 9 inches. Bake on the middle rack of oven for 15 minutes, or until edges are brown and top is dry but still slightly sticky. Do not overbake: Center of shortbread should still look underdone. Let shortbread cool for 5 to 10 minutes before serving warm, or cool completely for bar cookies.
For the Coriander Butterscotch: In a heavy 3-quart saucepan, melt butter over medium heat. Increase heat to high, add sugar, and stir to toast sugar for about 30 seconds. Add cream, whiskey, coriander, and salt, stirring to dissolve sugar. Bring sauce to a boil, stirring constantly for 5 to 7 minutes, or until a spoon leaves a dry trail across the pan. Set aside to cool slightly. If butterscotch hardens in saucepan, reheat on low, stirring in an extra tablespoon of cream.
For the Chocolate Topping: In a small saucepan, melt chocolate and butter together over low heat, stirring frequently to keep chocolate from burning. When chocolate is mostly melted, remove from heat and stir until no lumps remain.
To Serve as a Plated Dessert: Trim browned edges off warm shortbread and cut into even squares, placing each in center of a plate. Spoon warm butterscotch on top, then drizzle on chocolate topping. To drizzle, gather melted chocolate on a spoon and rapidly flick spoon back and forth about 8 inches over plate. Garnish with additional ground coriander, if desired. Serve warm.
To Make Bar Cookies: Spread butterscotch over completely cooled shortbread with an offset spatula. Refrigerate or freeze until butterscotch hardens, then spread cooled chocolate on top in a thin layer. Top with a sprinkle of ground coriander and refrigerate until chocolate is firm and glossy. Cut into 1-inch squares and serve or wrap in plastic before freezing.
Make-Ahead and Storage
Wrapped in plastic, the bar cookies will keep in freezer for 1 month.