Upside Down Key Lime Pies

For a fresh twist on a classic, try serving key lime pie upside down. Baked and served in individual ramekins, this custardy key lime filling packs a big flavor punch. After cooling and chilling, top with toasted graham cracker crust crumbs and fresh whipped cream. This is a simple, yet totally impressive and fun dessert to serve!

upside down key lime pie in custard cup

Typical dessert flavors this time of year: sweet potato, apple, caramel, pumpkin, spice.

Dessert flavors that make zero sense right now: key lime.

If you’re up for breaking tradition, consider these upside down key lime pies. The recipe yields only 4-6, which is convenient for smaller gatherings. They’re make-ahead, individually portioned, and just plain FUN. Plus, a light and refreshing dessert especially hits the spot after a heavier meal. Can we make key lime pie at Thanksgiving a thing?

key lime pie custard with whipped cream and graham cracker crumbles

Tell Me About these Upside Down Key Lime Pies:

We’re essentially baking a full key lime pie, only scaled down to fit a few custard cups. If you like key lime pie, you’ll go nuts for these.

  • Texture: The texture is like a full size key lime pie— smooth custardy filling, crunchy graham cracker crust, soft whipped cream. Plenty of satisfying texture in each bite.
  • Taste: Wham! Full-bodied tangy, yet sweet flavor hits your tastebuds like a windstorm. The tartness of lime is balanced with the sweetness in the crust and whipped cream.
  • Ease: Simple. The filling comes together with a mixer and you can break up the graham crackers with your hands. The only tricky part, if we can even call it that, is baking the custard cups in a water bath. Which, really, is just pouring hot water into a baking dish.
  • Serving: Serving desserts in individual cups seems fancier– almost like we’re dining at a restaurant. Everyone gets their own portion and you can get creative garnishing each with whipped cream, lime slices, raspberries, chopped nuts, etc. Feels extra special if you ask me.
  • Time: The filling comes together in minutes and baking is pretty quick too. The only things testing our patience are the cooling and chilling times. You can serve these once they cool to room temperature (about an hour), but they taste better if you chill them for an additional hour. Compared to other desserts, 2 hours isn’t so bad!

You Only Need 7 Ingredients

10 if you add homemade whipped cream.

  1. Egg Yolks: Egg yolks stabilize and set up the lime filling. Whip them until pale and thick before adding the other filling ingredients. (Whipped egg yolks pictured below on the right.) Whipped egg yolks create a lighter tasting filling.
  2. Lime Juice: Key limes are hard to find in certain regions this time of year. You can buy bottled key lime juice in most major grocery stores (I like Nellie & Joe’s brand) or you can just use regular lime juice, bottled or fresh-squeezed. You need about 5 regular limes to yield 2/3 cup juice. In this recipe, you won’t really taste a difference between key lime juice and regular lime juice.
  3. Sweetened Condensed Milk: One 14-ounce can of full-fat sweetened condensed milk (1) sweetens the dessert and (2) provides a smooth texture.
  4. Lime Zest: Optional, but if you’re juicing your own limes and have a zester, why not add a little extra flavor?!
  5. Graham Crackers: Make the “crust,” which goes on top after baking the filling, with graham crackers, brown sugar, and butter. Crush graham crackers with your hands or place into a zipped-top bag, seal, and crush with a rolling pin. We’ll toast everything together for a few minutes on the stove.
  6. Brown Sugar: For flavor, add a little brown sugar to the graham crackers.
  7. Butter: Butter helps the crust crumbles stay together.

egg yolks and whipped egg yolks

key lime pie custard filling

key lime pie filling in individual ramekins in a water bath

individual key lime pies in custard cups

graham cracker crust crumbles

Can I Make This with Lemons?

Yes! Swap lime juice for lemon juice and lime zest for lemon zest. Same process, bake time, and cool/chill times.


Whipped Cream or Meringue Topping

You can leave the upside down pies plain or add either of these toppings.

  • Homemade whipped cream kicks any dessert up a notch. You need heavy cream, sugar, and vanilla extract. Halve my recipe to make just enough. Mixing time remains the same. I used Wilton 8B piping tip to pipe whipped cream in these photos.
  • Instead of whipped cream, try marshmallow meringue. How convenient because you can use your 3 leftover egg whites to make it. Though I have a separate post for marshmallow meringue, follow the marshmallow meringue recipe and instructions in my s’mores brownie cupcakes. (That recipe uses 3 egg whites and makes the perfect amount for 4-6 individual key lime pies.)

individual key lime pie with whipped cream on top in a custard cup

3 Important Tips

  1. Individual Ramekins: These key lime pies are baked in individual oven-safe ramekins. I used these (affiliate link) 6 ounce oven-safe pyrex bowls. The recipe yields 2 cups of filling. Divide between 4 ramekins for a satisfying 1/2 cup serving (what’s pictured) or between 6 cups for a smaller 1/3 cup serving.
  2. Water Bath: Place the ramekins in a large baking/casserole dish or roasting pan, pour the filling evenly into each, then fill the pan with hot water. The water bath is essential because it creates a moist and humid environment, which helps cook the custard evenly and prevents ramekins (of any material) from shattering in the oven. This is how we cook crème brûlée and lemon pudding cakes, too. I have videos in both of those recipes if you want to watch this easy step.
  3. Bake Time: Be careful not to over-bake these individual key lime pies. Though the water bath prevents burning, the filling will taste rubbery if it’s cooked too long. Bake until the tops look *just about* set. Begin checking at 17 minutes. Though not necessary, you can also check the internal temperature. These are safe to eat when an instant read thermometer reads 160°F (71°C).
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upside down key lime pie in custard cup

Upside Down Key Lime Pies

  • Author: Sally
  • Prep Time: 15 minutes
  • Cook Time: 20 minutes
  • Total Time: 2 hours, 35 minutes
  • Yield: 4-6
  • Category: Dessert
  • Method: Baking
  • Cuisine: American

Description

These are fun individual servings of cool and custardy key lime pie! Cook the pies in individual custard cups in a water bath.


Ingredients

  • 3 large egg yolks
  • 2/3 cup (160ml) key lime juice*
  • one 14 ounce can full-fat sweetened condensed milk
  • 1 teaspoon lime zest
  • hot water for water bath

Crust

  • 2 full sheet graham crackers
  • 1 Tablespoon (15g) unsalted butter
  • 1 teaspoon packed light or dark brown sugar

Optional Toppings

  • whipped cream or meringue (see recipe note), lime slices, chopped macadamia nuts or pecans, raspberries, edible florals

Instructions

  1. Preheat oven to 350°F (177°C). Lightly grease four 6 ounce ramekins with butter or nonstick spray. See recipe note about other ramekin sizes. Place in a baking pan or small casserole dish. Four 6-ounce ramekins fit nicely into a 9-inch square bake pan. The pies will bake in a water bath inside the pan.
  2. For the filling: In a medium bowl using a handheld or stand mixer fitted with a whisk attachment, beat the egg yolks on medium-high high speed until pale and slightly thickened, about 3-4 minutes. Add the lime juice, sweetened condensed milk, and lime zest. Beat on medium speed until combined. You’ll have about 2 cups of filling. Pour evenly into prepared ramekins.
  3. Add water for water bath: Without splashing into the ramekins, slowly pour hot water into the casserole dish around the ramekins, about halfway up the sides of the ramekins. If it’s easier, you can transfer the casserole dish to the oven first, then carefully pour in the hot water.
  4. Carefully place the casserole dish/baking pan in the oven. Bake until the top of each is mostly set, about 17-20 minutes. When lightly tapped, the very center should only slightly jiggle. Though not necessary, you can also check the internal temperature. These are safe to eat when an instant read thermometer reads 160°F (71°C).
  5. Using tongs or an oven mitt, remove the pies from the water bath and place on a wire rack set over a baking sheet or kitchen towel to catch any dripping water. Cool pies for about 1 hour at room temperature, then chill in the refrigerator for 1 hour before assembling and serving. You can enjoy at room temperature, but they taste better if you chill in the refrigerator.
  6. Meanwhile, make the crust: As the pies cool, crush up the graham crackers with your hands or place in a zipped-top bag and crush with a rolling pin. Place butter in a skillet on the stove over low-medium heat. Add graham cracker crumbs and brown sugar. Stirring constantly, toast/cook for 4 minutes. Remove from heat and allow to cool.
  7. Assemble & serve: Sprinkle a couple spoonfuls of crust topping on each cooled pie. Before serving, top with whipped cream, meringue, or any desired topping. I used Wilton 8B piping tip to pipe whipped cream in these photos.
  8. Cover leftover pies tightly and refrigerate for up to 3 days.

Notes

  1. Make Ahead Instructions: Prepare the individual pies 1-2 days in advance. Bake and cool as directed. Cover each and chill in the refrigerator until ready to garnish and serve. I don’t recommend topping with whipped cream or meringue more than 6-8 hours in advance. (Refrigerate uncovered after topping.) Baked & cooled pies freeze well up to 3 months. Thaw overnight in the refrigerator.
  2. Lime Juice: Key limes are hard to find in certain regions this time of year. You can buy bottled key lime juice in most major grocery stores (I like Nellie & Joe’s brand) or you can just use regular lime juice, bottled or fresh-squeezed. You need about 5 regular limes to yield 2/3 cup juice. In this recipe, you won’t really taste a difference between key lime juice and regular lime juice.
  3. Ramekin Size & Bake Time: You need oven-safe ramekins to make this recipe. This recipe yields 2 cups filling, which is perfect for four 1/2 cup servings in (affiliate link) 6 ounce oven-safe pyrex bowls or six 1/3 cup servings in 4 ounce oven-safe bowls/ramekins with enough room for toppings. If using 8 ounce bowls/ramekins, only fill with 1/2 cup or 1/3 cup of filling. No matter if each is 1/3 cup or 1/2 cup, the bake time is between 17-20 minutes.
  4. Note for the crust: Want to skip the brown sugar and butter in the “crust” topping? Go ahead! Skip the toasting in step 6 and simply crumble graham crackers over each pie. You need about 1/2 cup graham cracker crumbs. If you don’t have graham crackers, use any similar cookie. Outside of the US? Use digestive biscuits.
  5. Whipped Cream or Meringue Topping: Halve my whipped cream to make just enough. Mixing time remains the same. Instead of whipped cream, try marshmallow meringue. How convenient because you can use your 3 leftover egg whites to make it. Though I have a separate post for marshmallow meringue, follow the marshmallow meringue recipe and instructions in my s’mores brownie cupcakes. That recipe uses 3 egg whites and makes the perfect amount for 4-6 individual key lime pies.

Keywords: key lime pie, lime

Sally's Pie Week

This recipe is part of Sally’s Pie Week, an annual tradition where I share multiple new pie recipes. If you’re looking for more inspiration, here are all of my pie recipes.

A few of my favorites are: chocolate chess pie, apple cranberry pie, lemon meringue pie, and banoffee pie.

25 Comments

  1. This looks like a delicious pie recipe! By any chance is there a substitute for SCM?

    1. Hi Emily, none that I’ve successfully tested. I would be cautious using an unsweetened thick milk/cream and adding granulated sugar, which would create a grainy tasting filling. Let me know if you test anything.

    2. Wendy McMurray says:

      These were so delicious! Easy too!

  2. This is a cute idea. My grandson loves your Key Lime Pie recipe, I am anxious to make this one for him!

    1. I hope your grandson loves this version just as much, Marilyn!

  3. Would this still work with a regular pie plate or springform pan?

    1. Hi Martha! Here is my full size key lime pie made in a pie dish.

      1. Thank you!

  4. Sally, hi, I’ve missed you. Hope your family is doing well and be sure to share some baby and big sister photos with us soon!
    Could you suggest a replacement for graham crackers in the crust. I have a honey allergy and can never find graham crackers made without honey any more. Thanks!

    1. Hi Judy! Maybe crushed Nilla Wafers, biscoff cookies, or gingersnaps work? Unsure if those contain honey. Any crunchy cookie you’re able to eat would work!

      1. I’ll try vanilla wafers. The recipe sounds great.

  5. Would it be possible to double this recipe, or would you suggest making two batches separately? I previously made your lemon pudding cakes which were amazing, I can’t wait to try these!

    1. Hi Brianna, doubling shouldn’t be an issue. Extend the whip time for the egg yolks, possibly to 5 or 6 minutes since you’re working with more.

  6. Possibly Graham crackers made for babies might omit honey in the ingredients. For anyone with a honey allergy that may be worth pursuing.

  7. Hey Sally!
    Question, Would this pie taste good with any other crust?

    1. Maybe Nilla Wafers or biscoff cookies? I also love crushed gingersnap cookies with key lime pie. Awesome contrast of flavors that surprisingly work well together.

  8. Hi, Sally!

    Yay! A new recipe! I am super excited for your Pie Week this year! I wish I could make all of them!
    Thank you so much for all that you do to get these recipes out! I always look forward to reading them!
    I hope you and your family stay safe and healthy in these troubling times!
    Have a great day!

    1. Thanks so much for the sweet note 🙂 Happy Pie Week!

      1. Happy Pie Week! 😀

  9. These look so yummy! I’m happy to find another use for my ramekins, too. I bought a bunch when I made your lemon pudding cakes for my mom’s birthday earlier this year and haven’t used them since.

    1. Sounds like a perfect plan, Sera – let me know how these turn out for you!

  10. I’m excited to try these using GF graham crackers for my daughter-in- law who has an allergy. Thanks for posting! For the lady who has the honey allergy, what if you try using Ritz crackers instead of graham crackers. Could also bake small circles of pie crust that would fit on the top of the baked key lime pies?

  11. I made these this week and they were fantastic! I just used regular lime juice, but next time will get some limes because I think the zest would elevate it that much more. The marshmallow topping might be my favourite part, but the whole pie was delightful and so smooth and creamy. Delightful!

    1. Thrilled to hear you enjoyed these, Thomas! Isn’t the marshmallow meringue topping an incredible pair to the key lime flavor? Thank you for giving this recipe a go!

  12. These were so delicious! I juiced regular limes and made the marshmallow meringue as the topping. I was really surprised at how easy the whole process was. The taste was amazing too, especially the next day. Will definitely save this recipe for the future!

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