If you’re a fan of tangy desserts that pack a punch of flavor, you’re in for a treat with these 3-Layer Key Lime Pie Bars. With a buttery crust and a luscious key lime filling topped with a cloud of mascarpone whip, these sweet bars capture all the zesty, creamy goodness of a traditional key lime pie, but in a handy, bite-sized form that’s perfect for any occasion!

What are Key Lime Pie Bars?

Our key lime pie bars are your new best friend when it comes to tangy, creamy, and utterly irresistible desserts. Imagine all the zingy goodness of a classic key lime pie, but in a fun, portable bar form. These bars start with a buttery, crumbly crust made from Biscoff cookies and graham crackers, which provides the perfect base for the smooth, luscious key lime filling. The filling itself is a dreamy, custard-style mix of egg yolks, sweetened condensed milk, and fresh key lime juice, delivering that signature tart and sweet flavor with all of the creaminess you crave from this style of pie.

But wait, there’s more! To top it all off, these bars get a generous dollop of mascarpone whip – a luxurious blend of mascarpone cheese, heavy cream, and powdered sugar. This creamy topping adds a rich, velvety layer that balances the tartness of the lime perfectly. Finished with a sprinkle of fresh lime zest, each bite of these bars is a refreshing burst of summer sunshine. Whether you’re bringing them to a picnic, serving them at a dinner party, or just indulging at home, key lime pie bars are sure to become your go-to summertime sweet treat.

Ingredients You Need

For the Crust:

  • Package of Biscoff Cookies – These cookies bring a caramelized, spiced flavor that perfectly complements the tangy lime filling.
  • Crushed Graham Crackers – Adding graham crackers gives the crust a classic texture and a hint of honey sweetness.
  • Unsalted Butter, Melted – This binds the crust together and adds a rich, buttery flavor that’s completely irresistible.

For the Filling:

  • Egg Yolks – Egg yolks give the filling its signature creamy, custardy texture.
  • Sweetened Condensed Milk – This adds sweetness and a silky, luscious consistency.
  • Key Lime Juice (or Juice from Large Limes) – Fresh lime juice provides that essential tangy, citrusy kick.
  • Key Lime Zest – Zest amps up the lime flavor and adds the most lovely fragrance.
  • Pinch of Salt – Just a touch sprinkle of salt will balance all the sweet and tart flavors.

For the Mascarpone Whip:

  • Mascarpone Cheese – This adds a rich, creamy texture to the whip topping.
  • Heavy Cream – Whipped to perfection, it makes the topping light and airy.
  • Powdered Sugar – Sweetens the whip without making it grainy.
  • Lime Zest, for Garnish – A sprinkle on top adds a burst of color and extra lime flavor.
A three layer key lime pie bar topped with a Biscoff cookie.

How to Make this Key Lime Pie Bars Recipe

  1. Prepare the Crust. Place the cookies and graham crackers in a food processor and crush until they form a fine crumb. Then drizzle in the melted butter while pulsing until combined. Transfer the mixture to the prepared pan and form an even layer. Bake briefly and allow to cool. 
  2. Make the Filling. After zesting and juicing the limes, add the egg yolks and lime zest to a bowl and use an electric mixer with the whisk attachment to beat them until thickened before adding the sweetened condensed milk and continuing to beat. Then, use a rubber spatula to fold in the lime juice and salt. 
  3. Bake Again. Spoon the filling into the crust, ensuring that the top is smoothed. Bake briefly until the filling has only a slight jiggle left to it before removing it from the oven and allowing it to cool completely. Once cooled, refrigerate for several hours to allow it to completely set. 
  4. Prepare the Topping. Place the mascarpone cheese and powdered sugar into a medium bowl and beat until smooth. Add the heavy cream and beat on a low speed before increasing it until stiff peaks form. Add lime zest, if desired. 
  5. Put it All Together. Spoon the whipped mascarpone on top of the bars and spread it evenly before refrigerating. 
  6. Serve. After chilling for at least half an hour, slice the bars, garnish with lime zest, and serve or store.

Variations

  • Limes – Not able to find key limes? You can use standard limes instead, but just avoid using bottled lime juice.
  • Crust – While we love Biscoff cookies, you can skip them in the crust and use solely graham crackers instead. Or, add some warm, spicy flavor by using crushed ginger snaps instead of Biscoff cookies. 
  • Spices – Add warm flavor to the crust with a few dashes of cinnamon. 
  • Coconut – Sprinkle some fresh coconut into the crust mixture for some tropical flavor. 
  • Chocolate – Drizzle some melted dark chocolate or white chocolate over top. 

Can I Store Leftovers? 

Leftovers? We’re not familiar with those in our house when we make these citrusy bars! But, if you do have to stash some of these away to save for later, it’s easy enough to do! 

Just place these key lime bars in an airtight container or wrap them in plastic wrap and store them in the refrigerator for 3-4 days. 

While you can safely freeze these for up to 3 months, their texture won’t be the same so we don’t recommend it. 

More Sweet and Citrusy Recipes

On the search for more sweets with a citrusy kick? We’ve got you covered with these recipes that pack a punch of tangy goodness!

Egyptian Mint Lemonade

Strawberry Lemon Bundt Cake

Creamy Lemonade

Copycat Starbucks Lemon Loaf Recipe

Overhead image of key lime pie bars topped with Biscoff cookies.

A 3-layer key lime pie bar.

3-Layer Key Lime Pie Bars

No ratings yet
Author: Food Dolls
Servings: 12 servings
Prep: 15 minutes
Cook: 15 minutes
Chill Time: 3 hours 30 minutes
Total: 4 hours
These key lime pie bars feature a buttery crust, creamy filling, and a mascarpone whip topping in bite-sized bars!

Ingredients  

For the Crust:

  • 1 8.8 ounce package Biscoff cookies
  • 1/2 cup crushed graham crackers (half of a sleeve)
  • 8 Tablespoons unsalted butter melted

For the Filling:

  • 6 egg yolks room temp
  • 1 can sweetened condensed milk 14 oz.
  • 2/3 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
  • 1/3 cup powdered sugar
  • 1 1/4 cup heavy cream
  • Lime zest for garnish

Instructions 

Preheat the Oven:

  • Preheat your oven to 350°F (175°C). Line an 11×7 inch baking pan with parchment paper.

Make the Crust:

  • Crush the Biscoff cookies and graham crackers in a food processor until they form fine crumbs. Stream in the melted butter and pulse until combined. The mixture should look coarse and sandy.
    1 8.8 ounce package Biscoff cookies, 1/2 cup crushed graham crackers, 8 Tablespoons unsalted butter
  • If you don’t have a food processor, place the cookies in an airtight bag and crush them using a rolling pin or heavy-bottomed skillet.
  • Pour the crumb mixture into the prepared pan and press it into an even layer using a flat-bottomed glass or measuring cup.
  • Bake the crust for 10 minutes. Remove from the oven and set aside to cool.

Prepare the Filling:

  • Zest and juice the limes.
  • Using an electric mixer with the whisk attachment, beat the egg yolks and lime zest on high speed for 2-3 minutes until slightly thickened.
    6 egg yolks
  • Add the sweetened condensed milk and beat on high speed for 1-2 minutes until thick and voluminous.
    1 can sweetened condensed milk
  • Turn off the mixer and add the lime juice and a pinch of salt. Stir with a rubber spatula until combined, making sure to incorporate any zest stuck to the whisk.
    2/3 cup key lime juice or juice from 4 large limes, 2 teaspoons key lime zest, Pinch of salt

Bake the Filling:

  • Pour the filling over the crust and smooth the top.
  • Bake for 10-15 minutes until the center is mostly set but still slightly jiggly.
  • Remove from the oven and let cool to room temperature, then refrigerate for at least 3 hours or overnight.

Make the Mascarpone Whip:

  • Using a mixer, beat the mascarpone cheese, and powdered sugar for 30 seconds, or just until creamy. Pour in the heavy cream, and start the mixer on low and beat until combined. Slowly increase the speed and beat until stiff peaks, be careful not to overmix or the mixture will curdle. Add lime zest for garnish.
    4 ounces mascarpone cheese, 1 1/4 cup heavy cream, 1/3 cup powdered sugar

Assemble and Serve:

  • Spread the whipped cream over the chilled key lime pie bars in an even layer.
  • Refrigerate for an additional 30 minutes before slicing.
  • Garnish with more lime zest and enjoy!
    Lime zest

Equipment

1 (11×7) Baking Dish
1 Electric Mixer

Notes

  • If you can’t find key limes, regular limes (Persian limes) work well. Avoid using bottled lime juice for the best flavor.
  • If you prefer, graham crackers can be used for the crust. Use 3 cups crushed, and consider adding a touch of cinnamon for added warmth. Or, you can sub for 1.5 packages of Biscoff cookies.
  • Store the key lime pie bars in the refrigerator for up to 3-4 days.

Nutrition

Serving: 1serving | Calories: 486kcal | Carbohydrates: 38g | Protein: 7g | Fat: 35g | Saturated Fat: 18g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 6g | Trans Fat: 0.3g | Cholesterol: 166mg | Sodium: 84mg | Potassium: 181mg | Fiber: 0.2g | Sugar: 30g | Vitamin A: 955IU | Vitamin C: 5mg | Calcium: 142mg | Iron: 1mg

Nutrition information is automatically calculated, so should only be used as an approximation.

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Meet Alia & Radwa

Welcome to Food Dolls! We’re so glad you found us. We are Alia and Radwa, sisters who want to share simple and easy recipes with you. We hope you find recipes here that you enjoy making as much as we do! Learn more about us!

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