Sweet and tart, these irresistible and easy key lime pie bars are an awesome summer treat. This key lime bars recipe doesn’t need a lot of ingredients and comes together quickly. It also makes plenty to bring to a summertime gathering but can be pared down for a smaller family serving.
Key lime desserts are almost always a super tasty summer favorite. These key lime pie bars are basically a large key lime pie cut into squares. While my best key lime pie recipe uses most of the same ingredients, this version is made a little more simply with ingredients that can be found year-round as well.
I love a good bar recipe, because they can make a bunch of handheld pies to serve a lot of people. This recipe for key lime squares is like my creamy limoncello lemon bars, but instead of a shortbread crust, these use a graham cracker crust like my key lime pie recipe. Instead of topping with powdered sugar though, I recommend whipped cream here.
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🥘 Ingredients
I keep this recipe simple and easy with only about 8 ingredients including the crust, and a pinch of cinnamon is optional.
Graham Crust
Graham Crackers – You’ll need about 18 full sheets here for the graham cracker crumbs, which should be two packs if they have 9 in each. If you live outside the US where graham crackers can be hard to find, use digestive biscuits instead. 18 sheets are roughly 270 grams, so use that amount of crushed digestive biscuits.
Sugar – You can use all white granulated sugar here, but I like to add in a little bit of brown sugar as well.
Butter – Salted or unsalted is fine, and it doesn’t need to be room temperature because you’re going to melt it anyway.
Cinnamon – Optional, but I like to add just a pinch to the crust, about a ¼ teaspoon.
Key Lime Filling
Condensed Milk – Use two 14-ounce cans of sweetened condensed milk for the filling here.
Key Lime – Unlike my best key lime pie recipe, where I call for the zest and juice of actual key limes, I keep things easy here by using two substitutes. Use two regular limes for fresh lime zest and bottled key lime juice for the filling. Nellie and Joe’s makes a great product that is sold in most grocery stores, either near the lemon and lime juice, or by the alcohol where they sell non-alcoholic mixers. If you’d like to use real key lime juice and zest, feel free to do so.
Eggs – Use about 6 eggs here. Most recipes use all yolks, but here I use 4 yolks and 2 whole eggs. I find it gives just a slightly better texture in a 13x9 version. If halving the recipe for an 8x8 version, just use yolks.
🔪 How to Make
These easy key lime pie bars are simple to make and come together quickly in less than an hour. However, you’ll want to let them cool and refrigerate a few hours before serving. If making for a party, I’d recommend starting that morning or the night before so they can chill and set properly.
Preheat your oven to 350°F / 280°C. Prepare a 13x9 baking dish by greasing it or spraying it and lining it with a parchment sling down the long side.
Crush the graham crackers in a zipper lock bag (not sealed shut) with a meat mallet or rolling pin and dump into a mixing bowl. Add both sugars and cinnamon and whisk together. Pour the melted butter over top of the mixture and whisk together again until a crumbly, sandy mixture forms. This can also all be done with a food processor if you prefer.
Pour the graham cracker mixture into the prepared 13x9 baking dish and spread around and press down into the dish until evenly covered. Use a dry measuring cup bottom to help flatten it out evenly if it helps. Place into the preheated oven and par bake the graham crust for 10 minutes and set aside.
While the crust is heating, prepare the key lime filling. In a large mixing bowl, add the eggs and egg yolks and whisk well until no streaks of egg white remain. Add the sweetened condensed milk and whisk until fully combined. Now add the key lime juice and zest and continue whisking until it no longer looks separated, and everything is well combined.
When the crust comes out of the oven, you can add the key lime filling right away, no need to wait for it to cool first. Pour the key lime filling over the graham cracker crust and use a large spoon or spatula to make sure it covers the crust corner to corner and creates an even layer. Return to the oven and bake for another 15-20 minutes.
The key lime pie bars are cooked when the center just barely jiggles anymore. Remove from the oven and set the baking dish on a cooling rack to cool to room temperature, about an hour or so. Once cooled, cover and place in your refrigerator for at least 2-3 hours, or overnight.
When ready to serve, remove from fridge and lift the key lime bars out of the baking dish with the parchment sling. Use a sharp knife to cut into squares and top each bar with extra lime zest, thinly sliced limes, or fresh whipped cream if you prefer.
📖 Variations
Different Crusts
I love graham cracker crusts for key lime pie bars because they’re traditional, but you can easily swap things up as well.
Nutty Crusts – Add crushed pecans, almonds, or macadamia nuts into the graham crust for a nice flavor addition. I use macadamia nuts in my key lime pie recipe and they’re amazing in the crust.
Gingersnap – Instead of graham crackers, use gingersnap cookies. They add a great alternative flavor to graham crackers, like in my pumpkin swirl cheesecake. You’ll need about 270 grams worth of cookies.
Pretzels – For a slightly sweet and salty crust, use about 2 ½ cups of crushed pretzels instead of graham crackers.
Fresh Key Lime
If you want to make these with fresh key limes instead of bottled juice, you can, it will just take a bit more work. You’ll need a good 30-35 key limes to make 1 cup of juice, and the zest from 10-12 key limes.
💭 Frequently Asked Questions
Key limes are smaller than a standard Persian lime, with a thinner skin and a slightly floral note to their flavor. They’re also slightly more acidic, giving them a tarter and more intense flavor than regular limes.
Yes, you can. In most recipes for key lime desserts, you can swap fresh key lime juice for regular, fresh lime juice without a hugely noticeable difference. You’ll lose a little of a key lime’s floral notes and tarter favor, but most people wouldn’t taste the difference.
To get the cleanest slices on bar recipes, rinse a sharp knife under hot water and wipe clean between each cut. The hot water keeps the knife warm enough to slide through each slice cleanly.
🍽 Equipment
You don’t need any special equipment to make these easy key lime pie bars, but here’s a few items that deserve special mention.
Juicer – You don’t need a fancy juicing machine, but I do recommend a simple and cheap hand juicer for any recipe that requires juicing more than 1-2 fruits. The one listed is easy to use and collects the juice in a glass below. I then pour that through a fine mesh sieve into a measuring glass to remove any seeds or pulp that falls through. This is only needed if you wish to use fresh key limes or normal limes.
Baking Dish – In almost all fruit dessert recipes that require baking, especially recipes where the fruit contacts the dish, I recommend using glass or ceramic coated baking dishes. I prefer this 13x9 glass baking dish especially, and this 13x9 enameled baking dish from Staub. Metal baking pans can leave the finished dish with a slightly metallic taste.
Bowl Scraper – A cheap bowl scraper made of stiff but flexible plastic or nylon are amazing for recipes involving batters or doughs. I use one here because it contours to the shape of the mixing bowl to easily scoop out all the key lime filling and it helps to spread and level out the top layer.
❄️ Storage
Because they contain eggs and dairy, you’ll need to keep key lime pie bars refrigerated after serving. They’ll stay fresh for 3-5 days.
For longer storage, key lime bars do freeze well. You can store the entire batch in an airtight container for 2-3 months in the freezer. If freezing leftovers, cut lime bars, freeze them on a small sheet tray for about 30 minutes, then move to an airtight container and place wax paper between stacks to keep them from sticking together.
📋 Recipe
Easy Key Lime Pie Bars
Ingredients
Graham Cracker Crust:
- 18 sheets graham crackers, roughly 2 ½ cups crushed
- ⅔ cup white granulated sugar
- 2 tablespoons brown sugar, packed
- ¾ cup butter, melted
- ¼ teaspoon ground cinnamon, optional
Key Lime Filling:
- 2 14-oz cans sweetened condensed milk
- 1 cup key lime juice, fresh or bottled
- 2 tablespoons lime zest, or key lime zest
- 2 large eggs, at room temperature
- 4 large egg yolks, at room temperature
Directions
- Preheat your oven to 350°F / 280°C. Prepare a 13x9 baking dish by greasing it or spraying it and lining it with a parchment sling down the long side.
- Crush 18 graham cracker sheets in a zipper lock bag (not sealed shut) with a meat mallet or rolling pin and dump into a mixing bowl. Add ⅔ cup white sugar, 2 tablespoons brown sugar, and a ¼ teaspoon ground cinnamon and whisk together. Pour ¾ cup melted butter over top of the mixture and whisk together again until a crumbly, sandy mixture forms. This can also all be done with a food processor if you prefer.
- Pour the graham cracker mixture into the prepared 13x9 baking dish and spread around and press down into the dish until evenly covered. Use a dry measuring cup bottom to help flatten it out evenly if it helps. Place into the preheated oven and par bake the graham crust for 10 minutes and set aside.
- While the crust is heating, prepare the key lime filling. In a large mixing bowl, add 2 large eggs and 4 large egg yolks and whisk well until no streaks of egg white remain. Add 2 14oz cans of sweetened condensed milk and whisk until fully combined. Now add 1 cup of key lime juice and 2 tablespoons of lime zest and continue whisking until it no longer looks separated, and everything is well combined.
- When the crust comes out of the oven, you can add the key lime filling right away, no need to wait for it to cool first. Pour the key lime filling over the graham cracker crust and use a large spoon or spatula to make sure it covers the crust corner to corner and creates an even layer. Return to the oven and bake for another 15-20 minutes.
- The key lime pie bars are cooked when the center just barely jiggles anymore. Remove from the oven and set the baking dish on a cooling rack to cool to room temperature, about an hour or so. Once cooled, cover and place in your refrigerator for at least 2-3 hours, or overnight.
- When ready to serve, remove from fridge and lift the key lime bars out of the baking dish with the parchment sling. Use a sharp knife to cut into squares and top each bar with extra lime zest, thinly sliced limes, or fresh whipped cream if you prefer.
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