Key lime pie is a graham cracker crust filled with a baked mixture of sweetened condensed milk, egg yolks, and tart key lime juice, chilled until fully set. You bake it briefly so the acid and eggs firm the filling into a dense, custard like layer, then cool it completely before slicing.
The dish comes from the Florida Keys, where sweetened condensed milk became a kitchen staple in the 1800s because fresh milk was hard to keep on the islands before refrigeration, and small, intensely tart key limes grew locally in a way that regular Persian limes did not. Combining the two into a baked pie became a regional specialty long before it spread across the rest of the country, and it remains tied closely enough to Florida that it is the state's official pie.
Despite what a lot of restaurant versions serve, the real filling is pale yellow, not green, the green color comes from added food dye, not from the limes themselves.
What Actually Matters
The filling sets from acid, not gelatin. Key lime juice's acidity reacts with the egg yolks and sweetened condensed milk, firming the mixture into a sliceable custard once it's baked briefly and then chilled, no gelatin or cornstarch needed. Skipping the short bake and just chilling the raw filling leaves it thinner and less stable, since the heat is what locks the proteins in place. Real key lime juice, whether squeezed from actual key limes or a good bottled brand, also matters for flavor, key limes are more floral and slightly more tart than the Persian limes sold in most grocery stores.
Key Lime Pie Recipe (Serves 4)
Prep time: 3 hours 15 minutes (includes chilling). Cook time: 25 minutes. Total time: 3 hours 40 minutes.
- 3/4 cup graham cracker crumbs
- 3 tbsp unsalted butter, melted
- 1 tbsp granulated sugar
- 3/4 cup sweetened condensed milk
- 2 large egg yolks
- 1/2 cup key lime juice
- Whipped cream, for topping
- Lime zest, for garnish
- Preheat the oven to 350 degrees Fahrenheit. Mix the graham cracker crumbs, melted butter, and sugar, then press into a 6 inch pie pan.
- Bake the crust for 8 minutes, then let cool slightly.
- Whisk the sweetened condensed milk, egg yolks, and key lime juice together until smooth.
- Pour the filling into the crust.
- Bake 12 to 15 minutes, until the center is just set but still slightly jiggly.
- Cool to room temperature, then refrigerate at least 3 hours before slicing.
- Top with whipped cream and lime zest before serving.
Nutrition (Per Serving, Estimated)
| Calories | Protein | Fat | Carbs |
|---|---|---|---|
| 340 kcal | 6 g | 14 g | 48 g |
These numbers are a calculated estimate for the 4 serving recipe above, not a lab verified value.
Tips, Variations, and Storage
Bottled key lime juice works well and is far more practical than juicing the small, seedy fresh fruit, though real key limes give a slightly more floral note if you want to go the extra mile. Do not skip the bake, filling that only chills without going into the oven first tends to stay looser and less sliceable. A digestive biscuit crust is a reasonable substitute for graham crackers outside the United States. This pie is actually better made a day ahead, giving the filling plenty of time to fully set and the flavors to settle.
Frequently Asked Questions
Do I need real key limes, or is bottled juice fine?
Bottled key lime juice works well and is much more practical. Real key limes give a slightly more floral flavor but are small and tedious to juice in quantity.
Why is my filling not setting properly?
The acid in the lime juice needs heat to firm the eggs and condensed milk fully. Do not skip the bake, and make sure the pie chills long enough afterward, at least 3 hours.
Should key lime pie filling be green?
No, that is added food coloring. A real key lime pie filling is naturally pale yellow.
What can I use instead of a graham cracker crust?
A digestive biscuit crust is a close substitute in places where graham crackers are hard to find.
Can I make this pie ahead of time?
Yes, it is actually better made a day in advance so the filling sets completely and chills through.
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I'm Chef Alan. I have spent 35 years in professional kitchens, I have formal culinary education in New Hampshire, and I have been honored as a 6-Time 4-Diamond Chef. More about me here.
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