These 3-Layer Key Lime Pie Bars are a refreshing twist on the classic key lime pie, with a buttery, crunchy crust, a creamy lime filling, and a smooth mascarpone whipped topping. With vibrant lime flavors and a melt-in-your-mouth texture, these bars are a perfect treat for any occasion—whether it’s a summer barbecue or a family gathering. They’re easy to make and sure to be a hit!

Why You’ll Love This Recipe

These Key Lime Pie Bars are not only bursting with the zesty flavor of fresh key limes, but they also feature three delicious layers that complement each other perfectly. The Biscoff cookie crust adds a hint of spice and crunch, while the creamy lime filling is smooth, tangy, and perfectly sweet. The mascarpone whip topping is the finishing touch that makes these bars irresistible. Plus, they’re easy to make, and the chill time allows the flavors to meld together for the perfect balance of sweetness and tartness.

3-Layer Key Lime Pie Bars

Ingredients

For the Crust:

1 8.8-ounce package Biscoff cookies
½ cup crushed graham crackers (about half of a sleeve)
8 tablespoons unsalted butter, melted

For the Filling:

6 egg yolks (room temperature)
1 can (14 oz) sweetened condensed milk
⅔ cup key lime juice (or juice from 4 large limes)
2 teaspoons key lime zest
Pinch of salt

For the Mascarpone Whip:

4 ounces mascarpone cheese
⅓ cup powdered sugar
1 ¼ cup heavy cream
Lime zest, for garnish

(Tip: You’ll find the full list of ingredients and measurements in the recipe card below.)

Directions

To Make the Crust:

Preheat the Oven: Preheat your oven to 350°F (175°C). Line an 11×7-inch baking pan with parchment paper for easy removal of the bars.
Crush the Cookies: In a food processor, combine the Biscoff cookies and graham crackers. Pulse until finely crushed. If you don’t have a food processor, place the cookies in a ziplock bag and crush them with a rolling pin.
Combine with Butter: Add the melted butter to the cookie crumbs and pulse until combined. The mixture should be sandy and slightly moist.
Press the Crust: Pour the crumb mixture into the prepared pan and press it firmly into an even layer using the back of a glass or measuring cup.
Bake the Crust: Bake for 10 minutes. Remove from the oven and let it cool.

To Prepare the Filling:

Zest and Juice the Limes: Zest the limes first, then juice them.
Beat the Egg Yolks: In a stand mixer or using a hand mixer, beat the egg yolks and lime zest on high for 2-3 minutes until slightly thickened and pale in color.
Add the Sweetened Condensed Milk: Pour in the sweetened condensed milk and beat on high for another 1-2 minutes until the mixture is thick and fluffy.
Add Lime Juice and Salt: Turn off the mixer and add the lime juice and a pinch of salt. Stir with a rubber spatula to combine, scraping down the sides of the bowl to incorporate any zest stuck to the whisk.

To Bake the Filling:

Pour and Smooth: Pour the filling over the cooled crust and smooth it into an even layer.
Bake: Bake for 10-15 minutes, or until the center is set but still slightly jiggly. Remove from the oven and let it cool to room temperature, then refrigerate for at least 3 hours or overnight.

To Make the Mascarpone Whip:

Whip the Mascarpone: In a mixer, beat the mascarpone cheese and powdered sugar for 30 seconds until creamy.
Add Heavy Cream: Gradually add the heavy cream, starting on low speed and increasing the speed until the mixture thickens and forms stiff peaks. Be careful not to overmix, or it may curdle.
Add Lime Zest: Fold in some lime zest for extra flavor.

To Assemble and Serve:

Spread the Mascarpone Whip: Once the bars have chilled, spread the mascarpone whipped cream over the top in an even layer.
Chill for 30 More Minutes: Refrigerate for an additional 30 minutes to allow the layers to set properly.
Garnish and Serve: Before serving, garnish with extra lime zest for a burst of color and fresh flavor.

Storage:

Store in an airtight container in the fridge for up to 4 days.

Servings and Timing

Servings: 8-10
Prep Time: 15 minutes
Cook Time: 15 minutes
Chill Time: 3 hours 30 minutes
Total Time: 4 hours

Tips & Variations

Extra Zing: Add a small amount of lime juice (about 1-2 teaspoons) to the mascarpone whip for an extra tangy finish.
Make It Vegan: Use a dairy-free alternative for the mascarpone cheese and heavy cream, like coconut cream, for a vegan version.
Crust Options: You can use graham cracker crumbs exclusively if you prefer a more classic crust, or even try chocolate cookie crumbs for a unique twist.
Add a Crunch: If you like a bit of crunch, top with some toasted coconut flakes or crushed nuts for added texture.

Storage/Reheating

Storage: Store the bars in an airtight container in the fridge for up to 4 days.
Reheating: These bars are best served chilled, so no reheating is needed. Simply enjoy them straight from the fridge!

FAQs

1. Can I use regular limes instead of key limes?

Yes, you can use regular limes if key limes are not available, but key limes do have a slightly different flavor that makes them ideal for this recipe.

2. Can I freeze these bars?

Yes, these bars freeze well. Once set and garnished, wrap them tightly in plastic wrap and foil. Freeze for up to 2 months. Thaw in the fridge overnight before serving.

3. Can I make this dessert ahead of time?

Yes, this dessert is perfect for making ahead. In fact, it tastes even better after chilling for a few hours or overnight.

4. Can I add more lime zest to the filling?

Yes, feel free to add more lime zest to the filling if you love a stronger lime flavor.

5. Can I use a different topping instead of mascarpone whip?

You can substitute mascarpone with whipped cream or cream cheese for a lighter topping, but mascarpone gives a richer, creamier finish.

6. Can I make this gluten-free?

Yes, this recipe is naturally gluten-free as long as you use gluten-free graham crackers or another gluten-free cookie for the crust.

7. How do I know when the filling is done baking?

The filling should be set on the edges but still slightly jiggly in the center. It will firm up as it cools.

8. Can I make these bars without a stand mixer?

Yes, you can use a hand mixer or even beat the egg yolks and filling by hand, but a stand mixer will make the process quicker.

9. Can I add a fruit topping to these bars?

Yes! Fresh berries or a fruit compote would make a great topping for added flavor and color.

10. How long do these bars need to chill?

They should chill for at least 3 hours to set properly, but overnight is best for the most flavorful and firm texture.

Conclusion

These 3-Layer Key Lime Pie Bars are the perfect blend of tangy lime, creamy mascarpone, and a crunchy, buttery crust. Whether you serve them as a sweet treat for a party or a refreshing dessert on a warm day, they are sure to be a crowd favorite. With a smooth filling, a hint of lime, and a delicious topping, these bars are a must-try for any key lime pie fan!