March 14 may be a celebration of pi, the mathematical constant, but it's also the perfect excuse to enjoy some pie, the dessert. Not that you need an excuse when you can whip up a key lime pie as easy and delicious as this one from the legendary steakhouse Morton's of Chicago (its bright green color also makes it perfect for St. Patrick's Day this weekend). And while you indulge in a slice (or wait for the pie to come out of the oven), catch up on the surprising history of pie – it wasn't always as appetizing as it is today.

Key Lime Pie

Ingredients

1 10-inch Keebler Graham Cracker "Ready Crust"
1 oz egg whites (approximately one egg)
28 oz sweetened condensed milk (2 cans)
6 tbsp sugar
1 cup egg yolks (approximately 12 eggs)
8 oz "Realime" Lime Juice
2 tbsp powdered sugar
1 cup heavy cream
1 lime (if desired)

Directions

1. Heat oven to 375 degrees. Remove plastic cover from pie crust and brush inside with egg whites. Bake the crust for 5 minutes. Remove and set aside. Keep oven on.

2. Combine milk, sugar, egg yolks, and lime juice in a mixing bowl. Whip by hand until smooth and sugar has dissolved. Pour mixture into pie crust. Fill to the rim, being careful not to spill over the edge. 

3. Place pie in oven and bake for approximately 30 minutes, or until center is firm. Remove from oven and place in refrigerator. 

4. Meanwhile, place the cream and powered sugar in a mixing bowl. Use an electric mixer to whip on high speed until very stiff. 

5. Take chilled pie out of the refrigerator. Serve each slice with a dollop of whipped cream or place whipped cream in the center of the pie and spread to the edges of the crust; the whipped cream in the center of the pie should be equal in depth to the filling and taper off to the edges of the pie. If desired, grate lime zest over whipped cream.