My favorite desert is a key lime pie, though I only recently discovered it in the last few years. It's a simple pie: lime juice, egg yolk, and sweetened condensed milk, mixed and poured into a graham cracker crust. The topping is either meringue or whipped cream, though 'purists' insist on meringue, which I also prefer. I gather wars are fought over the topping in certain circles.
Key lime pie started in Florida, of course. Milk spoiled quickly in the heat and humidity, so people used canned milks for much of their cooking. When sweetened condensed milk was created by Borden's, people experimented with it by adding the juice of the small, acidic key limes–native to the state. The juice was acidic enough to curdle the milk; combined with the yolks, the mixture creates a thick, yellow custard.
The pies originally weren't heated, except to brown the meringue on top. With today's risk of salmonella, though, the pies are usually heated in a 300 to 350 degree oven for 10-15 minutes.
It is difficult to make a genuine key lime pie, because most juice sold as key lime juice is really a concentrated form of persian limes. One recipe I read began with, "If you want to make real key lime pie, you must travel to Florida, preferably in the winter. Quickly make friends with one or more people who have a key lime tree in their back yard. Then beg, beg like a yankee…"
Though Florida does sound good right now, I made do with the bottled "Key West key lime juice", which is the concentrated persian.
For being a simple recipe, there are a great number of recipes for key lime pie. I eventually settled on a simple 3 yolk, 14 ounce sweetened condensed recipe. I began with 2/3 cups juice, which I quickly abandoned after the first attempt. The next was a half cup, and it wasn't bad, but still too tart.
My ideal recipe ended up being 3 ounces key lime juice, 3 egg yolks, and the tin of condensed milk. I beat the egg yolks until nice and lemony looking, and then blended in the milk until well mixed. I added the juice, mixing just until thoroughly mixed and poured the custard into a graham cracker crust.
I baked the pie 'naked' in a 350 degree oven for about 12 minutes. While the pie was baking, I whipped the egg whites, saved when separating out the yolks for the pie, until soft peaks formed. I then added 1/4 teaspoon cream of tartar and 1/2 teaspoon vanilla. I continued to beat the egg whites at high speed, adding 6 tablespoons of sugar gradually, beating at the end until all the sugar is dissolved and firm peaks are formed. I don't overbeat, and the egg whites are still moist, creating a creamy meringue. This is critical: you have to have a creamy meringue.
I layer the meringue over the hot pie filling, spreading evenly and sealing to the edges of the pie. The pie goes back into the oven another 10 minutes until the top is light brown.
It has to sit out for an hour, and then in the fridge for at least two. The recipe makes a small pie, but what a pie. I'd, uh, post a picture but, um, it seems to be gone.
