If you love Key lime pie, or just lime-flavoured desserts in general, you’ve got to try these triple-layer bars. Simply put — you’re going to love them! They’re everything you love about the classic pie, in bar form. From the buttery graham cracker crust, to the lush and silky sweet-tart key lime filling flecked with lime zest, to the blanket of barely sweetened whipped cream spread over top, you don’t want to let summer pass by without making a batch.
Can I Use Regular Limes Instead of Key Limes?
These rich bars get their signature zingy, sweet-tart flavor from Key lime juice. You can start with bottled key lime juice, like Nellie & Joe’s Key West Lime Juice, or fresh Key limes (you’ll need about 25 to 30). But if you can’t get your hands on Key limes or juice, you can easily substitute regular limes (you’ll need about 10 medium limes). When made with Persian limes, the bars will have a slightly more zippy, acidic flavor.
The Difference Between Key Limes and Regular Limes
There are a few differences between Key limes and Persian, or regular, limes. The first thing you’ll notice is that Key limes are much smaller in size. What makes Key limes such a great choice for desserts is that they’re more aromatic with a sweeter, less acidic taste. Key limes also happen to have seeds, while Persian limes do not.
Tips for Serving Key Lime Pie Bars
You’ll want to give the Key lime pie bars plenty of time to chill in the fridge — a minimum of four hours (up to overnight). This is why I like to make them a day in advance any time I plan on serving them. Making sure the filling is cold and rinsing your chef’s knife a couple of times while cutting the bars will help ensure you get clean slices.
For the crust:
- Cooking spray
- 6 tablespoons unsalted butter
- 12 5 Ball Road full-size graham crackers (about 6 1/2 ounces), or 1 1/2 cups graham cracker crumbs
- 2 tablespoons granulated sugar
- 1/4 teaspoon kosher salt
For the filling:
- 1 to 2 medium limes
- 2/3 cup key lime juice (from 25 to 30 key limes)
- 1 (14-ounce) can sweetened condensed milk
- 5 large egg yolks
- 1/4 teaspoon kosher salt
For the topping:
- 1 cup cold heavy cream
- 1 tablespoon powdered sugar
- Arrange a rack in the middle of the oven and heat the oven to 350ºF.
- Lightly coat an 8×8-inch metal baking pan with cooking spray.
- Line the bottom and two sides with parchment paper, leaving an overhang of about 2 inches on the sides to form a sling.
- Make the crust. Place 6 tablespoons unsalted butter in a small microwave-safe bowl. Microwave in 20-second bursts until mostly melted, 40 to 50 seconds total (it will melt completely as it sits). (Alternatively, melt the butter in a small saucepan over medium heat.) Set aside to cool slightly.
- Break 12 full-size graham crackers into rough pieces and place in a food processor fitted with a blade attachment. Add 2 tablespoons granulated sugar and 1/4 teaspoon kosher salt. Process until the crackers are the texture of sand, about 15 seconds. Add the melted butter and pulse to combine, 10 to 12 pulses. (If using graham cracker crumbs, just stir the crumbs and butter together in a bowl.)
- Transfer the mixture to the prepared pan. Using your hands or the bottom of a measuring cup, press into the bottom of the baking pan in an even layer.
- Bake until fragrant and starting to darken around the edges, 12 to 15 minutes. Meanwhile, prepare the filling.
- Make the filling. Finely grate the zest of 1 to 2 medium limes until you have 3 teaspoons. Save the zested limes for another use. If needed, juice 25 to 30 key limes until you have 2/3 cup juice.
- Place 2 teaspoons of the lime zest, lime juice, 1 (14-ounce) can sweetened condensed milk, 5 large egg yolks, and 1/4 teaspoon kosher salt in a large bowl. Whisk until well-combined, smooth, and pale yellow. Pour over the crust and spread in an even layer (it’s okay if the crust is still warm).
- Bake until the filling is just set and still a little jiggly in the center, about 15 minutes. Let cool completely on a wire rack. Cover and refrigerate for at least 4 hours or up to overnight.
- Make the topping. Place 1 cup cold heavy cream in the bowl of a stand mixer (or large bowl if using an electric hand mixer). Beat with the whisk attachment on medium speed until barely thickened, 1 to 3 minutes. Add 1 tablespoon powdered sugar and continue beating until stiff peaks form, 1 to 2 minutes more.
- Run a knife around the edges of the pan. Grasping the parchment sling, lift the key lime bar slab out of the dish and onto a cutting board.
- Spread the whipped cream over the bars. Garnish with the remaining 1 teaspoon lime zest. Cut into 16 squares and serve chilled.
Key lime substitutes: If you can’t find key limes, juice about 10 Persian limes or use an equal amount of bottled key lime juice instead.
Storage: Leftover cars can be covered and refrigerated for up to 4 days.
Originally published in thekitchn.com