I thought nothing of driving 6856 km from Victoria, BC to Key West, Fl. in order to find an authentic Key lime pie, and the key, I discovered talking to the local experts, is the lime. You must use authentic Key lime (citrus aurantifolia), not the more common, bigger, greener, sweeter, cheaper Persian limes which were introduced in Key West after the native Key lime was destroyed and eradicated by a hurricane in 1926. Certainly, Key lime on the label does not mean grown in Florida as I have found that in January, there are no Florida-grown limes anywhere. Both the Key lime and the Persian lime varieties come from Mexico.
It is usually best to keep recipes simple, so I will follow the directions of the Key West Key lime pie recipe postcard. It calls for 1/2 cup of lime juice, a can of sweetened condensed milk, 4 large egg yolks. They say to mix the yolks and the condensed milk and to add the juice slowly stirring until the filling is smooth and creamy. At this point, you have 3 options, the postcard has no use for the egg whites, some recipes use them to make a light meringue to cover the filling, but I chose to beat 3 of them hard and to gently mix them into the filling at the end. After that, pour the filling in a graham cracker crust and cook for about 25 minutes at 350 F. Check with the tip of a knife, if the knife comes out clean, it’s done. Cool for 20 minutes, then refrigerate two hours before eating. Sprinkle and decorate with whipped cream and limes as you wish!
Condensed milk is the basic for the original recipe because early in the 20th century there was no refrigeration on the Florida Keys to preserve milk or cream. William Curry, a shipping magnate, invented the recipe to sell his imported cans of condensed milk. It has later been proven to make a smoother filling than cream although some people contend that a filling with Vanilla ice-cream was President Truman’s favorite.
On a final note, the pie should be yellow, if it is lime colour, this is a sure sign that it contains food colouring and should be disdained.
We found the pie to be quite sweet, but not as sweet as the restaurants’ versions. If you like it tart, make sure to use the small Key limes which are more acidic, and use only 3/4 can of condensed milk and an extra egg yolk.
Note: Sally Cole, who spends her winter in Florida, suggested using ginger snaps instead of Graham crackers for a more intense flavour.