Celebrate Pi (π) Day with Key Lime Pie

Meryl Streep in Heartburn
Anyone else remember this priceless scene?

As you may have heard, today is Pi Day, which is a celebration of the all things Pi.

π (which is generally represented by the greek letter) is pronounced Pi in English, of course.  The symbol for π is commonly used to represent the irrational number 3.14159.  The never ending number is generally rounded to 3.14, which is also today’s date, March 14th.  And that, my friends, is how Pi Day came about.

If it’s been a while since you worked with the number π or calculated circumferences of circles (which was Pi’s original use), you might be thinking:

“Math hurts my head.  Can’t we just celebrate Pi Day with regular ole pie?”

I’m all for that idea!

So today–in celebration of all things Pi–I am re-blogging a delicious recipe from my friend Natalie at The Genetic Chef.

By the way, Natalie–a fellow New Englander with roots in Peru and Italy–is a first class chef and posts the most envy-worthy photos of food you will ever see.  Check out her blog here: The Genetic Chef

Natalie’s recipe for Ultimate Key Lime Pie is phenomenal and the perfect dessert for this snowy New England day!


What are Key Limes?

Because I am well and truly stuck in my house and only had Persian limes available, my Key Lime Pie is a bit of a misnomer.  Key Limes, as the name suggests, are a hybrid lime cultivated in the Florida Keys.  Now I suppose I could have waded out to my car in search of bottled Key lime juice, but I’m pretty much snowed in this morning.  (Twenty two inches of snow and my snow shoveler is no where to be found!)

Key limes are indeed different than the limes you usually find in most grocery stores.  They are smaller and seedier than their Persian relatives.  Key limes are also more acidic–basically tart-er–than the Persian variety.  The special tartness of the Key limes might be why the original recipe did not require you to cook the filling.  The acid from the Key limes was originally used to thicken the canned milk.  Since Key Lime Pie was often prepared by fishermen at sea, there is a great benefit of not having to cook this pie. But for the modern cook, relying on the acid to thicken the filling without cooking is just not reliable or safe.

Why make Key Lime Pie?

The original recipe for Key Lime Pie often included a meringue topping similar to Baked Alaska, but I prefer whipped cream on mine.  I guess I prefer the whipped cream topping because of the very memorable scene in Nora Ephron’s film Heartburn, where Meryl is topping her Key Lime Pie with whipped cream when she confronts her cheating husband–spectacularly played by Jack Nicholson–and then proceeds to go into labor!  Anyone else remember that one?


 Key Lime Pie

Ingredients for the crust:

  • 9 whole graham crackers (usually one sleeve), crushed into crumbs or the equivalent
  • 5 tablespoons melted butter

Ingredients for the pie:

  • 2 -14 ounce cans sweetened condensed milk
  • 2 whole eggs, beaten
  • 3/4 cup Key Lime juice or equivalent (read my note above)
  • 1/2 cup sour cream
  • 1/8 teaspoon salt

Ingredients for the whipped cream topping:

  • 1 cup heavy cream
  • 2 tablespoons powdered sugar




  1. Preheat the oven to 350 degrees.
  2. Spray pie plate with non-stick spray or grease with butter
  3. Combine the graham crackers and melted butter in a bowl and pour into pie plate.  Spread the cracker crumbs with your fingers or the bottom of a glass until they evenly cover the bottom and sides of your pie plate.
  4. Bake crust for 10 minutes in preheated oven and set aside.  Keep your oven on.
  5. While your crust is baking, combine the milk, sour cream, eggs, juice and salt and whisk until silky smooth.
  6. Pour the filling onto the baked graham cracker crust and carefully put the pie into the oven.  Cook for ten minutes.  You might be tempted to cook this for longer than 10 minutes, but don’t.  Yes, the filling will still be a bit jiggly in the center.
  7. Make the topping by combining the cream and sugar and whisking until thickened and you see soft peaks.
  8. Just before you are ready to serve dessert, spread the whipped cream over the pie.  Garnish with a twisted lime slice if desired.  Natalie suggests freezing the pie for 30 minutes before cutting, if you want a more dramatic presentation.  Or you could smoosh the finished pie into Jack Nicolson’s face and go into labor like Meryl did.  It’s up to you!
Table Talk Pie Tin
I’m using my old school Table Talk Pie tin! Guess I’m not getting the deposit back!


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