Traditionally, Key lime pie is made from Key limes, also known as Mexican or West Indian limes. They're smaller and seedier than conventional limes and their aromatic juice more sour. Combined with super-sweet condensed milk, egg yolks and a graham cracker crust, that juice makes a terrific pie.
These dessert bars are the traditional pie's less fussy but equally irresistible buddy. Go ahead and use Key limes if you've got them, but the limes available in most grocery stores, called Persian or Tahitian limes, will work beautifully, too. They're also considerably less work to juice. You'd need about a dozen Key limes to get the 3/4 cup of juice you need for these bars, whereas you'll need only about six conventional limes. And - purists, avert your eyes - if you're short on time, you can use bottled Key lime juice. Just check the ingredients before you buy: You want 100% juice without added sugar.
For the crust, vanilla wafer cookies step in for the classic graham crackers. Either cookie would work just fine, but the vanilla in the cookies complements the floral notes of the lime juice nicely. To finish, the bars are topped with lightly sweetened whipped cream. The cream tames the lime's acidity and is less finicky than meringue.
Super simple to make and travel-friendly, these bars beg to be taken to your next (responsibly distant) picnic, no plates or silverware required. Cut them before you leave the house to make sharing easy, but bring the heavy cream and confectioners sugar, unwhipped, in a jar. (Keep both the jar and the bars chilled, if possible.) Just before serving, make a big show of shaking the jar to whip the cream and spoon it onto the individual squares. Then sit back and feign exhaustion while the praise rolls in. You'll look like you've earned it.
Key Lime Pie Bars With Vanilla Wafer Crust
Yield: 16 servings
Total time: 45 minutes, plus chilling
For the crust:
1 (11-ounce) box vanilla wafers
2 tablespoons granulated sugar
8 tablespoons unsalted butter, melted
For the filling:
1 3/4 cup condensed milk (1 14-ounce can plus 1/2 cup)
5 large egg yolks
3/4 cup Key lime or conventional lime juice
1 teaspoon lime zest
For the topping:
1 cup cold heavy cream
1 tablespoon confectioners sugar
Heat oven to 350 degrees. Line a 9-inch square pan with parchment paper, leaving a 2-inch overhang on two sides. In a food processor, combine vanilla wafers and sugar, and pulse until you have fine crumbs. Add butter, and process until evenly moistened. Transfer mixture to prepared pan, and press it down into an even layer. Bake until fragrant and a shade darker, 15 to 17 minutes.
Meanwhile, prepare the filling: In a medium bowl, whisk together condensed milk, egg yolks, lime juice and lime zest.
Pour filling over crust (it's OK if it's still warm) and bake until the filling is set, about 15 minutes. Transfer to a rack to cool completely, then cover and refrigerate for at least 4 hours.
Use a sharp knife to release edges. Using the parchment overhang, carefully lift and transfer the bar to a cutting board. Just before serving, whip heavy cream and confectioners sugar until soft peaks form. Top bars with whipped cream, and cut into 16 squares to serve.