Raspberry Key Lime Pie

It's been a long summer, and I only have two weeks at home before I have to head back up to Madison for the fall semester. It won't be too bad, though, since my current research project is studying key lime pie. I'm not allowed to say too much, but I will admit that I make a damn good key lime pie because of it. It's a perfect balance of sweet and tart, and it has an incredibly smooth, creamy texture.

Like most recipes, my key lime pie is delicious all on its own or with a dollop of whipped cream, but it gets exponentially better when you swirl in some fresh raspberry puree. It adds another element of acidity and a gorgeous pop of color. Since it's still basically raspberry season, I simmer some fresh raspberries with some sugar to break them down a bit and then puree them with some raspberry jam. If you want to make this year-round (which you will), just heat some raspberry jam with a little bit of water, whisk until smooth, and swirl into your pie base when cool.

I think the red raspberries contrast beautifully with the key lime pie (which definitely should not be green if you ask any Key West native or pie expert), but the recipe can work with just about any other berry. Deep purple blackberries would be gorgeous, or you can do a combination. I'd make two separate purees and drizzle them on top of each other instead of mixing for maximum aesthetic appeal.

As for the pie itself, it starts with a graham cracker crust. I tend to just buy a premade crust from the grocery store because it's easy and they don't shrink. It's definitely possible to make your own with graham cracker crumbs, butter, and sugar, but I find that they tend to shrink and burn.

Making the key lime pie filling is truly easy as pie (yes, that was a terrible joke). There are only four ingredients: sweetened condensed milk, egg yolks, a bit of extra sugar, and, of course, key lime juice. If you gain anything from this recipe, make it these two facts: key lime pie should never be noticeably green and regular lime juice is NOT an acceptable substitute for key lime juice.

You can choose to juice dozens of those teeny key limes (if you can even find them), or you can get bottles of key lime juice in many grocery stores or online. I cannot stress this enough; it is impossible to make a halfway decent key lime pie if you don't use key lime juice.

Once you obtain your key lime juice, whisk it with a can of sweetened condensed milk, a few egg yolks, and a little bit of extra sugar (optional if you don't want it quite as sweet). It forms a thick, velvety custard that I recommend baking immediately before the lime juice curdles the eggs, though of course there is time to swirl in that yummy berry puree. I bake my pies just until they set in the center; you don't want the top to brown, and you want a soft but not runny filling.

This is honestly the best key lime pie recipe you'll ever try. It has approval from undergrads, grad students, and professors in the food science department, so you know it has to be good. Add some fresh berries (and some homemade vanilla whipped cream) and it's literally the best pie--of any variety--that you'll ever have.

1 Graham Cracker Crust
1 14 oz Can Sweetened Condensed Milk
3 Egg Yolks
1/2 Cup Key Lime Juice
3 T Sugar
2 oz Raspberries
2 T Raspberry Jam
Whipped Cream

Combine the raspberries, 1 T sugar, 1 T water, and the raspberry jam in a small pot. Cook for 5 minutes or until thickened. Strain and set aside to cool.

Heat oven to 325F.

Whisk the condensed milk, egg yolks, lime juice, and sugar together.

Pour the key lime mixture into the crust and swirl in some of the raspberry puree. Bake for 16 minutes or until just set. When cool, garnish with the whipped cream.

Makes 1 9" Pie
Recipe Adapted from Nellie & Joe