How to Make Key Lime Pie

A tart, creamy filling made from four ingredients, in a buttery graham cracker crust. It's one of the easiest pies to get right.

Makes

One 9-inch pie, 8 slices

Active time

About 30 minutes

Bake

Crust 10 minutes; filling 15 minutes

Chill

At least 3 hours

Key lime pie is a Florida classic that needs no rolling pin. The filling thickens because the acid in lime juice reacts with the proteins in sweetened condensed milk and egg yolks. A short bake then sets it firmly and cooks the yolks. You can read more about the limes themselves in our Key lime vs. Persian lime guide.

Ingredients

For the crust

• 1 1/2 cups (150 g) graham cracker crumbs, about 10 full sheets
• 1/4 cup (50 g) sugar
• 6 tablespoons (85 g) unsalted butter, melted
• Pinch of salt

For the filling

• 1 can (14 ounces) sweetened condensed milk
• 4 large egg yolks
• 1/2 cup (120 ml) fresh Key lime juice, from about 20 to 25 Key limes or 4 Persian limes
• 1 tablespoon finely grated lime zest

For the topping

• 1 cup (240 ml) cold heavy cream
• 2 tablespoons powdered sugar
• Lime slices or zest, to garnish

Instructions

1. Make the crust. Heat the oven to 350°F (175°C). Stir the crumbs, sugar, salt and melted butter until the mixture looks like wet sand. Press it firmly into the bottom and up the sides of a 9-inch pie plate, using the bottom of a measuring cup to pack it tight.
2. Bake the crust. Bake for 10 minutes, until fragrant and slightly darker. Let it cool for at least 15 minutes. Leave the oven on.
3. Mix the filling. Whisk the egg yolks and lime zest for about a minute, until the yolks lighten slightly. Whisk in the condensed milk, then the lime juice. The mixture will thicken noticeably as you stir.
4. Bake. Pour the filling into the crust and bake for 15 minutes, until the edges are set and the center still wobbles slightly. It should not brown.
5. Chill. Cool on a rack for 30 minutes, then refrigerate for at least 3 hours, or overnight, until cold and firm.
6. Top and serve. Whip the cream with the powdered sugar to soft peaks. Spread or pipe it over the pie just before serving, and garnish with lime.

Common problems

• Crumbly crust that falls apart: it wasn't packed firmly enough, or needed a little more butter.
• Filling won't set: it needed more chilling time, or the juice was measured short. Acid is what thickens it.
• Weeping topping: whipped cream softens in the fridge. Add it shortly before serving.

Store Key lime pie covered in the fridge for up to 3 days. It also freezes well for up to a month, and some people prefer it served half-frozen.