Key Lime Pie is the ultimate symbol of food from Florida. Specifically, the Florida Keys. No one really knows when the first Key Lime Pies were made or who made them since there’s no documentation. However, according to historians, the most likely candidate is a ship salvager turned millionaire named William Curry. He had a cook known only as Aunt Sally. She supposedly created the pie in the late 19th Century.
Other historians believe that fisherman off the Keys, off to sea for long periods of time, created the pie as a way to help preserve their supplies, especially eggs.
Sweetened condensed milk was used because, until the Overseas Highway was built in 1930, there was a lack of fresh milk, ice, and refrigeration on the Keys. To this day, it is the key to making the pie so creamy.
The other main ingredient is, of course, key limes. The key lime tree is native to Malaysia and most likely arrived in the Keys in the 16th Century with the Spanish explorers. They are about the size of a golf ball with a yellow-green skin. Their juice is sweeter than the more common Persian limes.
As a fun little political aside, in 1965, Florida State Representative Bernie Papy, Jr. introduced legislation calling for a $100 fine to be levied against anyone advertising Key Lime Pie that isn’t made with key limes. The bill didn’t pass.
(Some historical information from whatscookingamerica.net)
Now, to the recipe.
Of course, the purist, like Rep. Papy, would say that the only true Key Lime Pie is made with fresh key lime juice. And they would be right. However, many of us don’t have access to fresh key limes, or, if we do, the time to juice & zest about 20 – 30 to make this pie.
I use a combination of fresh lime juice and bottled key lime juice. The most common brand of key lime juice is Nellie & Joe’s. However, if you can find fresh key limes, and have the time to prepare them, by all means, use them.
Another question is what kind of crust to use: pastry or graham cracker? My own personal preference is pastry. More specifically, cookie. Which is what I do in this recipe. And, because the crust recipe here is essentially a cookie recipe, it isn’t going to behave like a regular pie crust.
Meringue, whipped cream, or plain? Again, it’s up to the baker. I like meringue. It’s also most likely the original topping since heavy cream wouldn’t have been available in the Keys before the 1930’s. In this recipe I use an Italian Meringue. It’s made with a hot sugar syrup as opposed to granulated sugar. It makes an excellent, stable meringue that is almost reminiscent of a fluffy cake frosting.
One more thing. True Key Lime Pie doesn’t have green food coloring. The color of the pie should be a light yellow-green color. If you see a pie that has a fluorescent green hue, walk away. It’s most likely a pre-made mix.
Also, I prefer a more tart pie than many people. Many of the key lime pies I’ve tasted really put the emphasis on sweet rather than lime. I feel I’ve remedied that here. It’s more of a sweet-tart flavor.
Shortbread Cookie Crust
2c. (9 oz.) all-purpose flour
1 tsp. baking powder
1/2 tsp. salt
1 tbsp. citrus zest (optional)
1/2 c. light brown sugar
1 c. (2 sticks) unsalted butter, softened
Key Lime Filling
2 cans sweetened condensed milk (don’t use non-fat. Yuk.)
3 egg yolks
1 1/4 c. lime juice (I use a combination of fresh Persian lime & bottled key lime in this recipe. However, you can use all fresh of one or the other)
2 tbsp. lime zest
1 1/4 c. sugar
1/2 c. water
2 tbsp. light corn syrup (keeps the syrup from “sugaring up” or solidifying)
6 egg whites, room temperature
1/4 tsp. cream of tartar (if you don’t have this, it’s all right. However, it does act as a stabilizer for the whites)
1. Make the crust: Sift together the flour, baking powder, and salt into a small bowl. If you’re using the zest, toss that into the dry ingredients as well.
Weighing the flour.
Zesting the limes. The Microplane is a perfect tool for this. It takes off the outer peel while leaving behind the bitter white pith. If you don't own a Microplane, go get one.
The dry ingredients and zest mixed together.
2. In a mixer bowl, beat the butter and sugar together on medium-high speed until the mixture becomes light and fluffy.
The butter & sugar in the bowl.
Beating together the sugar & butter.
You want a fluffy, aerated mixture. This will help with the texture of the crust.
3. Turn the speed down to low and gradually add the flour mixture.
Adding the flour to the butter & sugar
Keep mixing until the flour is completely incorporated.
4. Turn the dough out onto a large sheet of plastic wrap and shape into a slightly flattened disk. Wrap the dough tightly in the plastic wrap, place in the refrigerator, and chill for at least 3 hours.
The dough ready for the refrigerator
Note: At this point, you can simply use this dough for cookies. Delicious.
5. After you’ve let the dough chill, take it out of the refrigerator and let it sit for about 15 – 20 minutes to let it soften slightly. When you roll out the dough, you want it to be firm but not rock-hard.
Dough ready for rolling.
6. Unwrap the dough and lay it on a floured surface and lightly sprinkle the top with more flour. Alternately, you can sandwich the dough between 2 pieces of wax paper or plastic wrap.
7. Roll the dough out, starting from the center and working out to the edges. Turn the dough a 1/4 turn each time you pass the pin over it. This will help make a more even thickness as well as, especially if you’re using a floured surface, keeping the dough from sticking. Use more flour if you need to, but try to use as little as possible. Too much flour will make the crust tough and dry.
Note: Again, remember, this is a cookie dough. It is not going to behave the same way as a regular pie dough. Because of the high butter content, this dough will get very soft, very fast as you work it. If the dough cracks while you’re rolling, just press it back together. If you give up on trying to roll it out (and believe me, I have a couple of times), you can simply take pieces of dough and press them into the pie plate. Trust me, though, the results are worth a little frustration.
Getting ready to roll the dough.
8. When you’re done rolling, take a 9-inch pie plate and measure the dough. There should be approximately 3 – 4 inches of extra dough around the outer edges of the pie plate.
Measuring the pie dough.
9. Now for the fun part. Carefully flip the dough onto the pie plate and shape the dough into the plate. Trim any dough overhanging the edges to a 1″ overhang. (if you don’t have any overhang, it’s all right.) Use whatever scraps you have to patch up any holes, tears, or spots and the edge that are a little short of dough.
Save the scraps for cookies.
Getting ready to flip the dough
A not entirely successful flip
If your dough looks like this after you've flipped it into the pie plate, don't despair. All will be well.
After a little repair work. See? I told you it all comes together.
10. Tuck under the overhang around the edges. (If you have any. The most important thing is that the crust is as even a thickness as possible.). Finish the edges as you like. Use a fork to prick a few holes in the crust and place it in the freezer for at least 30 minutes.
Pie crust ready for the freezer. Freezing the crust will help to keep it from melting & burning in the oven when you par-bake it later.
11. Meanwhile, preheat your oven to 350F. Grease a piece of foil or parchment paper on one side with spray. Set aside.
12. Take the pie crust out of the freezer, place it on a baking sheet, and press the foil or paper down into it. Fill the foil or paper with pie weights (i.e. dried beans, lentils, or rice) and place the pie crust in the oven.
Raw crust filled with pie weights ready for the oven.
13. Par-bake the crust for 30 minutes. Take the crust out of the oven, carefully remove the foil or paper and the weights. Wrap the edges in foil, if needed, and bake an additional 8 – 10 minutes.
Note: There will be a bit of melting of the crust, especially the outer edge. It’s inevitable given the fact this is cookie dough. When the crust comes out of the oven, it will be very soft and fragile. Hence, the cookie sheet.
Finished par-baked crust
14. Take the crust from the oven and let it cool completely. At this stage, of you like, once the crust is cool, you can carefully wrap it in plastic and place it in the refrigerator.
15. While the crust is cooling, you an make the filling. In a large bowl, whisk the egg yolks to break them up. Add the condensed milk, lime juice, and zest. Whisk until you have an even, well combined mixture. The filling will thicken upon standing. Set aside or cover and refrigerate.
Egg yolks & lime zest.
After adding the lime juice
After adding the sweetened condensed milk. Yummy stuff.
16. Once the crust has cooled completely, wrap the edges in foil (to prevent any further browning)
Carefully pour in the filling.
Ready for the oven.
Place the filled pie on the baking sheet (if you haven’t done so already) and put the pie back into a preheated 350F oven for 35 – 45 minutes. If your oven has a hot spot, and most ovens do, rotate the baking sheet about halfway through the initial baking time.
The center should be a bit wobbly when you take it from the oven. It will firm up as the pie cools.
Note: This is a very important thing to remember. When you are making ANY type of cream pie, you must pay attention to the baking time & doneness of the filling. I didn’t the first time around when I was making the pie for this post.
I had workmen in my house that day and became distracted. So, here is what happened:
What you don't want to see. An overcooked cream pie.
The overcooked proteins have basically squeezed out all the liquid causing the filling to separate.
So, what you’ll end up with, if you aren’t paying attention, is essentially sweet-tart scrambled eggs. And I’m fairly certain none of you will be going for that. The pie will still taste good, but the texture will be, well, funky.
Eat the pie yourself or dress it up and give it to someone you don’t like very much.
Here is what you want to see:
A smooth, creamy pie
Let the pie cool completely. (I usually cover it once it’s cooled and place it in the refrigerator overnight.)
17. Make the meringue: Separate the eggs using the 3-bowl method (see my blog post “Mom’s Favorite” on how to do this). Place the egg whites & cream of tartar in a mixer bowl and set aside.
Egg whites & cream of tartar ready to go.
Make the sugar syrup: In a medium saucepan, mix together the sugar, corn syrup, and water. Cook over medium heat, stirring until the sugar dissolves. Bring to a boil.
Sugar syrup getting ready to boil
18. Once the syrup reached 240F on a candy thermometer (soft ball stage):
Syrup at 240F
begin whisking the egg whites on high speed until they are frothy:
Frothy egg whites.
19. Once the sugar syrup reaches between 245F & 250F (firm ball stage), remove the saucepan from the heat.
Syrup at 250F. You don't want it to get any hotter than this or the whites will too stiff to work with later.
Turn the mixer down to medium speed. CAREFULLY AND SLOWLY pour the hot syrup into the whites, avoiding the whip.
Carefully pouring the sugar syrup into the whites.
(A hot syrup burn is really, really painful. There’s a reason pastry chefs call this stuff napalm. Do not give this to the kids to do, be sober, and pay attention.)
Once you have poured in all the sugar syrup, turn the mixer speed up to medium-high and continue whisking the whites until they are firm and shiny. The bowl should be just warm to the touch when they’re done.
Whisking the egg whites after all the syrup has been added
The finished egg whites. These could be used as a cake frosting at this point.
20. Turn your oven on to broil (you may want to take a rack out) or have a torch ready to go. I usually set my oven on “Broil” setting and turn the temperature to 450F.
21. Pile the meringue on top of the pie. Spread it all the way to the edge of the crust and smooth or spike it out as you like (there will be A LOT of meringue).
An almost comical amount of meringue.
Ready for the oven.
Place the pie in the lower part of the oven and let the meringue brown. Watch it carefully, though. It can burn quickly. About 60 – 90 seconds is all it will take.
If you have a torch, brown the meringue with that if you like. You can direct the heat more directly and make the browning more even.
A cross section. It was really, really good.
Store any uneaten pie, covered, in the refrigerator. It’ll keep for about 3 – 4 days.
P.S. Remember what I said about saving the scraps for cookies?
1. Line a baking sheet with parchment paper. Have your oven preheated to 350F.
2. Roll out the leftover dough into a 1/8 – 1/4″ thickness, depending on how crunchy or soft you like your shortbread cookies.
3. Cut the cookies out into your desired shape.
Cutting out cookies
4. Place the cut cookies onto the baking sheet about 1″ apart. If you like, sprinkle them with a little turbinado (raw) sugar before baking:
Ready for the oven
5. Bake the cookies for 8 – 10 minutes. Depending on the thickness and how brown you like them. Turn the baking sheet about halfway through the initial cooking time.
6. When the cookies are done, let them cool slightly on the baking sheet then transfer to a rack. The cookie yield depends on how much leftover dough you have and how thick you make the cookies.