Key lime pie is a tangy-sweet custard tart with a buttery graham cracker crust and a silky filling that sets just enough to hold its shape. The filling comes together with sweetened condensed milk, which sweetens and thickens it without baking, so the pie needs only a brief time in the oven to set the crust and warm the filling through.
Ingredients for Key Lime Pie
Graham cracker crumbs mixed with melted butter form a sturdy, sandy crust that won’t crumble when you slice. Sweetened condensed milk is the secret to the filling’s creamy texture and smooth sweetness without eggs or flour. Key lime juice brings the distinctive tartness that defines the pie, while egg yolks add richness and help the filling set just enough in the oven. A pinch of salt balances the sweetness, and sweetened whipped cream provides a cool, airy contrast to the dense, tangy filling.
Why This Key Lime Pie Works
Sweetened condensed milk is already thick and sweet, so the filling needs almost no cooking. Mixing it with tart key lime juice and egg yolks creates a custard that thickens slightly as it bakes, but stays creamy because the condensed milk does most of the work. The eggs are there to help the filling set and to add a silky mouthfeel, not to cook into a firm custard.
A short bake at moderate heat is all you need. The filling goes into the oven just warm enough to set the crust and to bring the eggs to a safe temperature, but not so long that the filling toughens or the crust burns. After it cools, the pie sits in the refrigerator where the filling firms up further as it chills.
Key Lime Pie Tips & Tricks
- Use fresh key lime juice if you can find it, or bottled key lime juice from the baking aisle, never regular lime juice, which tastes different and will throw off the flavor balance.
- Press the crust firmly into the pan with the bottom of a measuring cup so it holds together and bakes evenly without gaps.
- Bake just until the filling is set at the edges but still slightly soft in the very center when you gently shake the pan, then stop, or it will overbake and turn grainy.
- Chill the pie for at least 3 hours before slicing so the filling firms up enough to hold clean edges and the flavors meld.
Mistakes To Avoid
Overbaking the filling causes it to turn grainy and weep liquid at the edges. The filling should jiggle slightly in the center when you shake the pan, not look set all the way through. If it bakes too long, the eggs cook too much and the custard breaks.
Skipping the crust-bake step before adding the filling leads to a soggy bottom crust that never crisps. A few minutes in the oven before the filling goes in dries out the crust so it stays crunchy against the filling.
Using regular lime juice instead of key lime juice throws off the flavor completely. Key limes are smaller, rounder, and more tart than Persian limes, and the pie depends on that sharp, distinctive taste to balance the sweetness of the condensed milk.
Cutting the pie before it is fully chilled causes it to fall apart and look messy. The filling needs at least 3 hours in the refrigerator to firm up enough to hold a clean slice, and overnight is even better.
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Ingredients
- 1 1/2 cups graham cracker crumbs
- 5 tablespoons unsalted butter, melted
- 1 (14-ounce) can sweetened condensed milk
- 4 large egg yolks
- 1/2 cup key lime juice
- 1/4 teaspoon salt
- 1 cup heavy cream
- 2 tablespoons granulated sugar (100g)
- 1/2 teaspoon vanilla extract
Step-by-step Instructions
- Heat the oven to 350°F (175°C). Mix the graham cracker crumbs and melted butter in a bowl until it resembles wet sand.
- Press the mixture firmly into the bottom and up the sides of a 9-inch pie pan using the bottom of a measuring cup.
- Bake the crust at 350°F (175°C) for 5 to 6 minutes until it smells toasted and looks light golden, then remove it and let it cool slightly.
- Whisk together the sweetened condensed milk, egg yolks, key lime juice, and salt in a bowl until smooth and well combined.
- Pour the filling into the warm crust and smooth the top.
- Bake at 350°F (175°C) for 8 to 10 minutes until the edges are set but the center still jiggles slightly when you gently shake the pan. The filling should reach 160°F (71°C) when checked with an instant-read thermometer in the center.
- Remove the pie from the oven and let it cool completely on a wire rack for about 1 hour.
- Refrigerate the pie for at least 3 hours, or overnight, until the filling is firm enough to slice cleanly.
- Just before serving, whip the heavy cream with the sugar and vanilla extract until stiff peaks form.
- Slice the pie with a sharp knife dipped in hot water and wiped dry between cuts, then top each slice with whipped cream.
Frequently Asked Questions
Can I use bottled lime juice instead of key lime juice?
No. Regular bottled lime juice is made from Persian limes and tastes sharper and more one-note than key lime juice, which is softer and more complex. The pie depends on key lime juice for its signature flavor.
Can I make this ahead?
Yes. The pie can be made up to 2 days ahead and refrigerated, covered loosely with plastic wrap. Add the whipped cream topping just before serving.
Can I freeze key lime pie?
Yes. After it is fully chilled, wrap the whole pie tightly in plastic wrap and freeze for up to 1 month. Thaw it in the refrigerator overnight before serving.
Serving Ideas for Key Lime Pie
Serve each slice topped with a dollop of whipped cream to cool and soften the tartness of the filling. A thin wafer cookie on the side adds a light crunch that contrasts with the creamy pie. Iced tea or lemonade works well as a drink because the cold and tartness balance the sweetness of the condensed milk.
