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How to Make Key Lime Pie
Key lime pie combines a graham cracker crust with a simple filling of key lime juice, sweetened condensed milk, and egg yolks, then tops it with whipped cream. The magic happens when the acid from the limes causes the condensed milk to thicken without baking, though a brief stint in the oven sets everything perfectly.
- Total time: 3 hr 40 min
- Hands-on: 25 min
- Serves: 8
- Difficulty: Medium
Ingredients
- 1½ cups graham crackers
- ⅓ cup melted butter
- 3 tablespoons sugar
- 4 large eggs
- 1 14-ounce can sweetened condensed milk
- ½ cup fresh key lime juice
- 3-4 key limes
- 1 cup heavy cream
- 2 tablespoons powdered sugar
Step by step
- Make the graham cracker crust. Crush 1½ cups of graham crackers into fine crumbs. Mix with ⅓ cup melted butter and 3 tablespoons sugar. Press firmly into the bottom and sides of a 9-inch pie pan. Bake at 350°F for 10 minutes until lightly golden. Let cool completely.
- Prepare the filling. Separate 4 large eggs, setting whites aside. Whisk the yolks until smooth. Add one 14-ounce can of sweetened condensed milk and whisk until combined. Slowly add ½ cup fresh key lime juice while whisking constantly. The mixture will start to thicken immediately.
- Add the lime zest. Grate the zest from 3-4 key limes directly into the filling. This adds tiny bursts of concentrated lime flavor that make the difference between good and exceptional pie.
- Bake the pie. Pour the filling into the cooled crust. Bake at 350°F for 15 minutes. The center should still have a slight jiggle when you shake the pan gently. Remove and cool to room temperature, then refrigerate for at least 3 hours.
- Make the whipped cream topping. Beat 1 cup heavy cream with 2 tablespoons powdered sugar until soft peaks form. Don't overbeat. Spread over the chilled pie just before serving, or pipe decorative swirls around the edges.
Tips & troubleshooting
- Room temperature eggs mix more easily and create a smoother filling
- Roll the limes on the counter while pressing down before juicing to get more juice from each lime
- Strain the lime juice if you want an ultra-smooth filling without any pulp
- Cover the pie with plastic wrap pressed directly onto the surface to prevent a skin from forming
- Let the pie chill overnight for the cleanest slices and best flavor development
Variations
- No-Bake Version. Skip the baking step entirely. The acid will set the filling in the refrigerator after 4-6 hours. Results in a softer, more custard-like texture.
- Persian Lime Substitute. Use regular lime juice if key limes aren't available. You'll need about ⅓ cup since regular limes are less acidic. Add an extra teaspoon of zest to boost the lime flavor.
- Meringue Topping. Beat the reserved egg whites with ¼ cup sugar until stiff peaks form. Spread over the pie and brown under the broiler for 2-3 minutes, watching carefully to prevent burning.
Questions
- Why did my filling not set properly?
- Not enough acid is usually the culprit. Key limes are more acidic than regular limes, so if you substituted, you may need more juice. Also, make sure your condensed milk hasn't expired and that you mixed the ingredients in the right order.
- Can I make this pie ahead of time?
- Absolutely. The pie actually improves after a day or two in the refrigerator as the flavors meld. Just add the whipped cream right before serving to keep it fresh and voluminous.
- What's the difference between key limes and regular limes?
- Key limes are smaller, more acidic, and have a more complex flavor with floral notes. They're worth seeking out, but regular limes will still make a good pie with slight adjustments to the juice amount.
- How do I know when the pie is properly chilled?
- The filling should be firm enough that a knife inserted in the center comes out mostly clean with just a small amount of filling clinging to it. The surface shouldn't jiggle when you gently shake the pan.