Millionaire's shortbread—the bar cookie of shortbread topped with layers of caramel and chocolate—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.