A stable base of traditional buttery graham cracker crust is topped with a puckery custardy key lime filling and plenty of whipped cream to create a dessert perfect for a picnic, potluck, or a mental vacation to the tropical Florida Keys. These bars come together in no time, so they make a great weeknight baking project or no-hassle weekend treat!
Key Limes vs Regular Limes
Key limes are a citrus fruit that grow wild in the Florida Keys during the summer and early fall. Smaller and more tart than the Persian limes you find in most grocery stores, these tiny citrus fruits produce a tangy and floral yellow juice that balances nicely with sweet ingredients in these bars. I occasionally find bags of key limes in my local grocery store, and more frequently find bottles of key lime juice—you can use either for this recipe. But if key lime anything is nowhere to be found, feel free to substitute with regular limes. The final bars will be a little less tart, but perfectly delicious. And if you really want that added lip puckering tartness, add the juice from one lemon into the mix!
How to Make Key Lime Filling
You don’t need any special equipment to make this filling, just a large bowl and sturdy whisk. The tart lime juice is combined with sweetened condensed milk and egg yolks to create a rich and creamy custard-like filling.
How to Make the Perfect Whipped Cream Topping
I love these bars topped with a generous dollop of whipped cream and making it from scratch couldn’t be simpler. If you prefer a meringue topping for your bars, use the leftover egg whites to make swiss meringue. Here are a few tips to achieve an amazing whipped cream: Chill everything: Keep your heavy cream in the fridge right until you’re ready to whip. Stick the bowl and whisk (or whisk attachment) in the freezer 20 minutes before whipping. If using a hand whisk, wrap the handle in a clean dish towel before whipping to avoid freezing your fingers. Keep a close eye: Over whip heavy cream and you’ll wind up with butter (delicious, but not for our purposes today), so pay attention to what’s going on in your bowl. You’ll notice small bubbles before the cream starts to thicken, and then you want to watch for the different stages of peaks: soft, medium, and stiff. For these bars, I like to whip my cream to a medium-stiff stage (it holds its shape when you lift your whisk out of the bowl). Whip by hand: I know, I know. This seems like the ultimate arm workout but whipping by hand is the best way to keep an eye on your cream and avoid over whipping. Whipped cream will hold for up to 2 days in an airtight container in the fridge. It may deflate a bit over time, but you can easily re-whip it before dolloping atop your bars.
How to Make a Parchment Sling
The trickiest thing about making these bars may be removing them from the pan. The crumbly graham cracker crust and soft custardy filling make it difficult to simply turn the pan over, like you would for a cake or brownies. Enter the parchment sling. Lining your pan with a parchment sling will help you lift your chilled bars out of the pan without cracking the crust or smooshing the topping. Here’s how to make one:
Grease the pan (bottom and all four sides) with butter.Cut the parchment paper as wide as the pan in one direction, and long enough to hang over the sides in the other direction.Press the parchment paper into the bottom of the pan and up along the two overhang sides.After baking and chilling, use both hands to hold the parchment overhang to lift the bars out of the pan.
Cutting and Serving Key Lime Bars
As tempting as it is to bite right in as soon as they come out of the oven, it’s important to let your bars fully chill and set in the fridge—not only to ensure the custard can set into a creamy texture, but also to help you cut clean lines in your bars. Once the bars are chilled and ready to cut, grab a chef’s knife and run the blade under hot water for a few seconds. Dry the blade with a clean dish towel and cut the bars straight down (don’t drag it through). Repeat warming and drying the blade as needed. Once they’re cut, add a dollop of whipped cream, a sprinkle of lime zest, and take that bite!
How to Store Key Lime Bars
Store key lime bars on a plate or small tray in the fridge, covered with plastic wrap or foil for up to 3 to 4 days. I recommend storing whipped cream separately and waiting to top the bars until right before serving, to avoid it getting runny on the bars.
More Citrus Filled Dessert Recipes
Key Lime Pie Citrus Olive Oil Cake Lemon Shaker Pie Lemon Tart Lime Icebox Cookies
1 1/2 cups (150g) graham cracker crumbs (from about 12 full sheets) 2 tablespoons granulated sugar 1/4 teaspoon ground cinnamon 1/4 teaspoon kosher salt 6 tablespoons unsalted butter, melted, plus more for greasing
For the filling
6 large egg yolks 2 (14-ounce) cans sweetened condensed milk 4 teaspoons fresh key lime zest 1 cup key lime juice, from about 30 key limes Large pinch kosher salt
For the whipped cream
3/4 cup heavy cream 2 tablespoons powdered sugar Pinch salt
Garnish
1 teaspoon fresh lime zest
In a large mixing bowl, whisk the graham cracker crumbs, sugar, cinnamon, and salt together. Add the melted butter and use a rubber spatula to stir until all the crumbs are coated—the mixture should look like wet sand. Zest the limes. Set 4 teaspoons aside for the filling and 1 teaspoon aside for the garnish. Juice the limes to get 1 cup of lime juice. In a large mixing bowl, whisk the egg yolks, condensed milk, key lime zest, key lime juice, and salt together until fully incorporated into a smooth yellow custard. Once cool, cover the pan with plastic wrap and chill in the fridge for at least 2 hours or up to overnight. Use a whisk or electric mixer fitted with the whisk attachment (if using an electric mixer, start on a low speed and gradually increase to medium) to whip the cream. Once the cream starts to thicken, add the powdered sugar and salt. Continue whipping the cream until it forms medium-stiff peaks (the cream stands on its own when you remove the whisk). Grab a chef’s knife and run the blade under hot water for a few seconds. Dry the blade with a clean dish towel and cut the bars straight down (don’t drag it through). Repeat warming and drying the blade as needed to cut the bars. Cut the bars into 8 pieces. Top each bar with an even layer of whipped cream dolloped using a small spoon and a sprinkle of lime zest. Serve.
