Best Key Lime Pie Bars
These easy Key Lime Pie Bars combine a buttery graham cracker crust with a velvety smooth key lime custard made from just a few simple ingredients. The result? A perfectly tangy, sweet, slideable treat that’s ideal for parties, cookouts, or any night of the week.
Love key lime pie but don’t feel like wrangling a pie crust? These Key Lime Pie Bars are the low-effort, high-reward answer. All the tart, creamy flavor you love in incredibly easy hand-held dessert bar form.
We’re talking press-in crust, whisk-and-pour filling, and a short bake time. It’s everything you want in a summer dessert: bright, refreshing, make-ahead friendly, and EASY!
If you’ve been here long enough, you know I have a major soft spot for citrus desserts. My Lemon Pie and Lemon Pie Bars are two of my favorite dessert recipes. But I forgot about how easy it would be to convert them to lime flavored until a family trip last year to Key West! My kids loved key lime pie (especially the slices of pie dipped in chocolate!) so it was time to make a key lime version of the lemon pie bars.
Three of the many slices of key lime pie consumed during our trip to Key West.
While key limes have a unique floral citrus flavor, regular limes work just as well here. I always prefer using fresh juice over bottled (you may need to strain it first), but don’t stress if all you have is bottled juice—it’ll still be delicious. And bonus: this recipe only uses egg yolks, so it’s perfect if you’ve made meringue, macarons, or angel food cake recently and have yolks to spare.
Why You’ll Love This Recipe
- Bright, Tangy Flavor: Key lime juice gives these bars a refreshing citrus zing.
- No Pie Crust Fuss: A press-in graham cracker crust means no rolling or blind baking.
- Make-Ahead Friendly: These bars taste even better the next day and freeze beautifully.
- Perfectly Sliceable: The filling sets up firm enough for clean cuts—ideal for parties.
- Minimal Ingredients: Just a handful of pantry and fridge staples come together fast.
- Customizable Citrus: Swap key limes for regular limes or even lemons if needed.
Ingredients and Substitutions
- Graham Crackers: Use traditional honey graham crackers crushed finely, or swap for Nilla wafers, Biscoff, or gingersnaps. Finely crush the graham crackers by hand or using a food processor.
- Granulated Sugar
- Butter: Either unsalted or salted works in the crust.
- Egg Yolks: The egg yolks should be at room temperature before using.
- Sweetened Condensed Mik: Make sure you’re using sweetened condensed milk and not evaporated milk.
- Key Lime Juice: Fresh limes are best, but bottled will work. Regular lime juice is a great sub – or swap flavors completely and try lemon juice or grapefruit juice.
- Lime Zest
- Heavy Cream
- Powdered Sugar
How to Make Key Lime Pie Bars
- Make the crust: Stir together crushed graham crackers, melted butter, and sugar. Press firmly into a lined baking dish and pre-bake briefly to set.
- Prepare the key lime filling: Whisk together egg yolks, sweetened condensed milk, lime juice, and lime zest until smooth and creamy.
- Pour and bake: Pour the filling over the crust and bake just until the center is mostly set. Let the bars cool to room temperature before transferring to the refrigerator to avoid cracks.
- Chill thoroughly: Refrigerate for at least 2 hours (or overnight) before slicing.
- Slice and serve: Use a sharp knife, wiping between cuts for clean squares. Top with whipped cream and garnish with additional lime slices or zest.
Key Limes vs Persian Limes
Let’s talk limes. This recipe is called Key Lime Pie Bars for a reason—but what makes a key lime different from a regular lime? And can you substitute one for the other? (Spoiler: Yes, you can.)
Key limes (also known as Mexican or West Indian limes) are smaller, more aromatic, and more acidic than the standard Persian limes you’ll usually find in grocery stores. They’re rounder with thinner skin that yellows as they ripen, and they pack a big punch of tart, floral flavor. The juice has a distinctive sharpness and brightness that really shines in desserts.
The downside? Key limes are tiny and full of seeds, so juicing enough for a full recipe is a process. If you can find fresh key limes and are willing to do lots of juicing and straining, nothing beats the flavor. But for convenience, bottled key lime juice (like Nellie & Joe’s) is a solid substitute and widely available.
Can’t find either? Regular limes (Persian limes) are a perfectly good option. The flavor will be slightly less vibrant and floral, but your bars will still taste amazing. I often use fresh-squeezed Persian lime juice, and if I’m really going for flavor, I’ll toss in a little extra zest to compensate.
Sweetened Condensed Milk: The Secret to a Sliceable Custard
Key Lime Pie Bars are known for their smooth, creamy filling that holds its shape perfectly when sliced. But if you’ve ever made a traditional custard or pudding, you probably added flour or cornstarch to help it set. So what’s different here?
The magic lies in the chemical interaction between egg yolks and sweetened condensed milk. How does this work? It’s time for my favorite subject… kitchen chemistry!
Kitchen Chemistry
Sweetened condensed milk has a high sugar concentration and low water content compared to regular milk. This high concentration of sugar denatures the proteins in the egg yolks, causing them to unravel. When the filling is baked, the protein strands interact and form a gel-like network that thickens the custard as it cools.
This is also why it’s so important not to overbake. Once the edges look set and the center has just a slight jiggle, it’s done. The custard will continue to firm up as it cools resulting in that perfect creamy-meets-clean-slice texture.
Tips and Tricks for Perfect Key Lime Pie Bars
- Egg Yolk Temperature: Eggs are easier to separate when cold, so separate the eggs right out of the refrigerator but let the yolks come up to room temperature before adding to the filling.
- Zest First, Juice Later: It’s easier to zest whole limes before juicing them.
- Strain the Juice: Key lime juice has lots of tiny seeds and little bits of pulp, so strain the juice before adding it to the filling.
- Cool Before Chilling: Let the key lime pie bars cool to room temperature before refrigeration to prevent cracks along the surface.
- Cut with a Sharp Knife: For clean slices, use a sharp knife and wipe the blade clean between each cut. Bars can be cut into 9 very large squares or 16 smaller squares.
- Storage: Key lime pie bars can be stored covered the refrigerator for up to 5 days or frozen in an airtight container for up to 3 months. Thaw frozen bars in the fridge.
- Recommended Tools: Citrus Juicer | Fine Mesh Strainer | Microplane Zester | Kitchen Scale | 9×9-inch Baking Pan | Parchment Paper
More Pie Bar Recipes
Key Lime Pie Bars
These easy Key Lime Pie Bars combine a buttery graham cracker crust with a velvety smooth key lime custard made from just a few simple ingredients.
Ingredients
For the Crust:
- 1 1/2 cups (188 grams) graham cracker crumbs
- 1/4 cup (50 grams) granulated sugar
- 1/2 cup (113 grams) unsalted butter, emlted
For the Filling:
- 4 large egg yolks, room temperature
- 14 ounces (397 grams) sweetened condensed milk
- 1/2 cup (113 grams) Key Lime juice (2-3 key limes)
- 1 tablespoon Key Lime zest (about 1 lime)
For Topping:
- 1 cup (227 grams) heavy cream
- 2 tablespoons confectioners' sugar
- lime zest and lime slices
Instructions
- Preheat the oven to 350°F. Spray a 9x9-inch baking pan with non-stick cooking spray. Line the pan with parchment paper and then lightly spray the paper as well.
- Make the Crust: In a medium mixing bowl, stir the graham crumbs, granulated sugar and melted butter until the mixture has the consistency of wet sand and sticks together when gently squeezed. Press the mixture firmly into the prepared pan. Bake for 8 minutes, then remove from the oven to cool.
- Make the Filling: In a large bowl, whisk the egg yolks, sweetened condensed milk, key lime juice and lime zest.
- Bake the Bars: Pour the mixture over the partially baked crust. Bake for another 15-20 minute, until the filling is set around the edges but still jiggly in the center. Remove the bars from the oven and cool to room temperature, then transfer to the refrigerator for at least 2 hours (preferably overnight).
- Decorate the Bars: Before serving, make the whipped cream. Using an electric mixer or immersion blender with a whisk attachment, beat the heavy cream and confectioners' sugar on high speed until medium-stiff peaks form. Pipe the whipped cream onto the bars or spoon whipped cream and spread over the entire surface of the key lime pie bars. Refrigerate for 15 minutes before lifting the bars out the pan, cutting into squares, and garnishing with lime zest and slices. Serve immediately.
Notes
- Separate the eggs while the eggs are still cold, then let the yolks come up to room teperature before whisking into the filling.
- Key lime juice has lots of pulp, so strain the juice before adding it to the filling. Alternatively, use storebought key lime juice.
- Make sure the bars cool to room temperature before placing them in the refrigerator.
- For clean slices, use a sharp knife and wipe the blade clean between each cut. Bars can be cut into 9 very large squares or 16 smaller squares.
- Key lime pie bars can be stored covered the refrigerator for up to 5 days or frozen in an airtight container for up to 3 months. Thaw frozen bars in the fridge.
- Recommended Tools: Citrus Juicer | Fine Mesh Strainer | Microplane Zester | Kitchen Scale | 9×9-inch Baking Pan | Parchment Paper
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