How to Make a Perfect Key Lime Pie
It's easy as pie. Truly.
Fact: When asked, “What’s your favorite type of pie” approximately 80% of all humans will respond: Key. Lime. Pie.
OK, this may be more of a hyperbolic expression of my experiences than it is a fact, but key lime really does seem to be king. At least it does in the circles I run in.
If nothing else, I feel like it’s the pie I make more consistently than any other. It’s a popular request for birthdays around the office, and I know for a fact I’ve made key lime pies annually for at least the past six or so years (because my last two significant others both claim the classic as their hands-down favorite and apparently, I only date scorpios with a deep affinity for key lime pie). I tell you this because I want you to understand, that with every one of these key lime pies I’ve baked over the years, I’ve tried something a little different. I’ve been on a journey, friends—a journey for the perfect key lime pie.
For many iterations along my KLP journey, I insisted upon some sort of gussied up version (like sweetened condensed milk wasn’t good enough) that involved making key lime curd and creamy custard layers from scratch. That’s all well and good, but I think I must have been insecure and overcompensating or something at that point in my life. Because I eventually came to see that A.) a can of sweetened condensed milk is a blessed thing and B.) the utter ease factor of a sweetened condensed milk-based key lime pie is part of its magic. A significant part. So really, it just came down to finding the right formula.
The next chapter of my KLP journey consisted of taking bits of this recipe, adding ideas from that recipe, and trying out my own little twists in an effort to fashion my perfect key lime pie. And folks, I think I finally may have it. (Note: I only feel OK implying that this pie is “all that” because a handful of people whose mouths I trust have told me that this is the best KLP they’ve ever eaten; among them were mouths that have previously put me in tears because of their lack of hesitation in telling me that something I made sucked. Point being, I feel awkward tooting my own horn, but I feel confident that this pie is pretty darn good.)
Here’s the thing, it’s oftentimes best to just keep the classics, well, classic. If someone asks for a key lime pie on their birthday, chances are… they don’t really care if you reinvent the wheel. And they probably don’t even care that you know how to make key lime curd—whoop-dee-flipping-doo, it’s actually not as good (or pretty to slice) as the OG canned milk construct for KLP. So, the recipe below really is just your typical key lime pie format, similar to that which you’d find on the Carnation website, but with a few small ratio tweaks and enhancements, such as:
A doubled-up filling.
I can’t be the only person who’s felt consistently underwhelmed/disappointed when it came time to pour my key lime pie filling into the par-baked crumb crust to find that it barely came halfway up the sides. I could never understand this. The classic sweetened condensed milk KLP archetype instructs that you use a 9-inch pie plate… but if I’m using a glass (9-inch) Pyrex pie plate, which I feel is fairly common, one can of sweetened condensed milk + the proportional equivalents of the other key (lime!) ingredients doesn’t feel like enough to fill my pie shell. Which makes me sad. So for this pie, we’re busting out TWO cans of sweetened condensed milk and buddy, we are not looking back.
A crust that says, “There’s more to life than graham crackers.”
I know this isn’t the right thing to say, but I generally think there are better options out there for cookie crumb crusts than graham crackers. Like Biscoff cookies, a.k.a. airplane cookies! Seriously, let me tell you a story. One year, I baked my own graham crackers from scratch just to blitz them into crumbs for a key lime pie crust… and that crust, constructed with hours of my life, was fine. Just fine. But it couldn’t hold a candle to this one—which takes roughly 5 minutes to throw together. Much like filling, I also believe in a thicker crust. Further notes on this below.
More than a dollop of sour cream.
Obviously, I am not the first to discover that sour cream makes life better, but a key lime pie filling enriched with sour cream is a really good thing.
So here you go, I’ve marked a few more relevant notes about the making of this pie and provided a few friendly suggestions (but you do what feels right to you) for topping it off below. If you give this pie a try—say, for Pi Day later this week—snap a pic and let us know what you think using the hashtag #TryMyRecipes.
Perfect Key Lime Pie
For the Crust*
- 1 (8.8-ounce) pkg. Biscoff cookies
- 2 ounces roasted, salted macadamia nuts
- 1 ounce granulated sugar (about 2 tablespoons)
- 1/2 ounce instant dry milk powder** (about 2 tablespoons)
- 1/2 tsp. salt
- 8 Tbsp. unsalted butter, melted
For the Filling
- 2 (14-ounce) cans sweetened condensed milk
- 1/2 cup sour cream
- 4 large egg yolks
- 1 tsp. grated lime zest
- 3/4 cup plus 1 Tbsp. key lime juice***
1. Preheat oven to 350 °.
2. To prepare the crust, combine cookies and macadamia nuts in the bowl of a food processor; pulse until coarse crumbs form. Add sugar, milk powder, and salt; pulse to combine. Add melted butter; process until mixture is moist and clumps together easily. Press crumb mixture evenly along bottom and up sides of a (9-inch) glass pie plate.
3. Bake crust on center rack at 350° for 9 minutes; place on a wire rack to cool. Prepare filling while crust cools, leaving oven on. (The crust can be made and refrigerated up to 1 day in advance or frozen up to 1 week in advance; simply cool completely after baking and wrap with plastic wrap.)
4. To prepare the filling, whisk together the condensed milk, sour cream, and yolks in a large mixing bowl until combined; whisk in zest and juice. Place the pie plate onto a rimmed baking sheet and pour filling mixture into prepared crust. Carefully transfer to oven and bake at 350° until pie is just set (pie should still be slightly jiggly in the center), about 10 to 12 minutes. Cool completely on a wire rack. Cover pie and refrigerate at least 8 hours. Top as desired.
*I like my crumb crusts thick. I like there to be enough of the crumb mixture for me to build up a nice looking edge around the lip of the pie plate (and maybe drop a little on the floor like the klutz I am); that said, it you prefer a more delicate layer of crumb crust, you can easily get away with cutting the amount of cookies and salt in half, and the butter down to 5 tablespoons. Personally, I’d leave the amounts on the other ingredients as is.
**I like to include dehydrated milk in crumb crusts because this helps the melted butter really kick ass at it’s job of binding everything together, and it adds a very subtle touch of dairy depth. This is a little trick I picked up from seeing how Christina Tosi uses the ingredient in some of her recipes. That said, it’s not essential to making this recipe “work,” so if you don’t have it in your pantry and don’t feel like buying it, that’s A-OK. Just leave it out this time, but I’d highly recommend grabbing a box next time you’re at the store so you can try it next time. (It also really comes in handy when you completely forget that you’re out of milk until you’re standing in front of a cup of morning coffee that you desperately need… but desperately do not want to drink black.)
***If you have trouble finding key limes or bottle key lime juice, you can use a mix of roughly 1 part lemon to 2 parts lime juice (if you need concrete measurements, say 5 tablespoons lemon juice + 9 tablespoons lime juice). Here’s the thing, I’m already suggesting that you zest a regular ol’ Persian lime (which, again, this pie isn’t going to fall apart or taste like wet dog if you don’t… but the zest does make it better), because I for one am not about to hunch over those itty bitty key limes with my microplane and gingerly zest away, so no sweat if you go ahead and lean on your standard citrus for juice too.