Key Lime Pie

the pie the Florida Keys built out of what the schooners brought: Key lime juice and egg yolk stirred into sweetened condensed milk until the acid sets it, poured into a graham cracker crust and barely baked

Origin: United States

From the journey of Lime.

Key West at the end of the nineteenth century was a prosperous island town with a serious supply problem: no fresh milk, no dairy herd, no ice, and, in many households, no reliable oven. What it did have was the small West Indian lime that the Bahamian wreckers and spongers who settled the island had spread through the Keys, growing on bare coral rock where almost nothing else would, and the sweetened condensed milk that Gail Borden had patented in 1856 and that arrived by the case on every schooner. The pie is the meeting of the two, and it rests on a single chemical fact: when the acid of a Key lime is stirred into condensed milk with egg yolk, the proteins coagulate and the mixture thickens and sets on its own, with no heat required at all. The original pies were therefore never baked. Modern practice gives them a brief turn in a low oven, not to set the filling but to make the egg safe, and the crust is the crumbled graham crackers that also came in by boat. Two points of local dogma are worth respecting. A true Key lime pie is pale yellow, because the juice of a ripe Key lime is yellow, and a green one has been coloured; and the topping is a matter of settled dispute between meringue and whipped cream, on which no outsider should venture an opinion.

Ingredients

Crust

200 g graham crackers or digestive biscuits, crushed to fine crumbs
100 g unsalted butter, melted
40 g caster sugar
1 pinch fine sea salt

Filling

397 g sweetened condensed milk (one standard tin)
4 whole egg yolks
125 ml fresh Key lime juice (about 20 Key limes, or 12 ordinary limes)
2 tsp finely grated lime zest

Topping

300 ml double cream, well chilled
2 tbsp icing sugar
1 whole lime, thinly sliced, to decorate

Method

Heat the oven to 160°C (140°C fan). Mix the crumbs with the sugar, salt, and melted butter and press firmly into the base and up the sides of a 23 cm pie dish, using the back of a spoon or a flat glass. Bake for 10 minutes and cool.
Zest the limes before juicing them, then squeeze the juice and strain it. Key limes are small, hard, and full of pips; roll them under your palm first and expect to work through a large number.
Whisk the egg yolks with the lime zest in a bowl for 2 minutes, until pale and slightly thickened. Whisk in the condensed milk, then pour in the lime juice in a steady stream, whisking continuously, and keep whisking for 1 minute as the mixture visibly thickens.
Pour the filling into the cooled crust, smooth the top, and bake for 12 to 15 minutes, until the surface has lost its shine and the centre wobbles very slightly when the dish is nudged.
Cool to room temperature, then refrigerate for at least 3 hours and preferably overnight. Whip the cream with the icing sugar to soft peaks, spread or pipe it over the cold pie, and decorate with lime slices.

Notes

Key limes (Citrus × aurantiifolia) are small, yellow when ripe, thin-skinned, and markedly more floral and more bitter than the large green Persian lime; if you can find them, the pie is noticeably better, and if you cannot, ordinary limes with a squeeze of lemon come reasonably close. Do not add green colouring: a Key lime pie is pale yellow and Floridians are firm about it. The meringue version, made with the four leftover whites beaten with 120 g of caster sugar and browned in a hot oven for 8 minutes, is equally traditional and is what most Key West restaurants serve; the choice between meringue and cream is a local argument of long standing. The unbaked original, in which the filling is simply chilled until firm, is still made in the Keys and is excellent, but it should be attempted only with pasteurised eggs.

The Gastrographer

Name: Key Lime Pie
Prep time: 30 min
Cook time: 15 min
Total time: 4 h
Yield: 8
Cuisine: United States
Ingredients: 200 g graham crackers or digestive biscuits, crushed to fine crumbs; 100 g unsalted butter, melted; 40 g caster sugar; 1 pinch fine sea salt; 397 g sweetened condensed milk (one standard tin); 4 whole egg yolks; 125 ml fresh Key lime juice (about 20 Key limes, or 12 ordinary limes); 2 tsp finely grated lime zest; 300 ml double cream, well chilled; 2 tbsp icing sugar; 1 whole lime, thinly sliced, to decorate

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Journey Point Map Key

Ingredient originTrade or transit route

Became a culinary stapleColonial / trade control