Key Lime Squares

September 16, 2016
key lime square recipe

As soon as you take a bite of a key lime square you get a tangy, sweet, tart, refreshing mouthful all at once! On a warm day the chill and tartness is just perfect.

What’s the difference between key lime pie and key lime squares, you might ask? Not too much really but I really like this way of eating it as it is a more manageable size and you can pick it up with your hand if you want. It lasts longer in my experience (since it’s not a pie you feel like you need to eat all at once) and this sizing makes it easier for sharing!

The last time I made these I brought them with us for a weekend of mountain biking at the Kingdom Trails in Vermont with some of our friends. It was my first time there and it was awesome! The trails were quite different from those we normally ride around the Boston area and it flows more like a ski resort with trail signs and difficulty markings. These squares traveled well (in a cooler as you want to keep them refrigerated) – I put each in a cupcake wrapper and the flavor actually enhanced over a day or two.

key lime square recipe

What makes key limes, key limes? It is a quite a bit smaller than the typical lime you purchase in the store (Persian lime) and has a more unique flavor. The photo below shows one in a teaspoon for scale – it really is that much smaller! They originated in the Florida Keys (hence the name) but many are now grown in Mexico. When you buy them know that these actually are more yellow in color when ripe compared to the Persian lime that is green.

Because of the size it can be a bit more difficult to juice them (and you need to juice about 23 for this recipe). I actually cut each lime in half and then turned it inside out to get the most juice in the easiest way. I found it helpful to juice into a larger bowl so there was more room/ sides to collect the juice and then strain it through a fine mesh sieve into a liquid measuring cup.

key lime square recipe


Key Lime Squares

As soon as you take a bite of a key lime square you get a tangy, sweet, tart, refreshing mouthful all at once!

Prep Time 20 minutes
Cook Time 20 minutes
Total Time 4 hours 50 minutes
Servings 16 squares


Graham Cracker Crust

  • 5 tablespoons unsalted butter
  • 1+ cup 1 cup + 2 1/2 tablespoons ground graham cracker crumbs about one sleeve of crackers
  • 1/3 cup granulated sugar

Key Lime Filling

  • 25+ key limes 1 1/2 teaspoons finely grated zest, 2/3 cup juice, reserve remaining 2-3 whole limes for garnish
  • 3 egg yolks
  • 14 oz can sweetened condensed milk

Whipped Cream

  • 1/4 cup heavy cream


  1. Make crust: Preheat the oven to 350 degrees F. Melt the butter on the stove on low / medium heat. To grind the graham crackers I put them in a food processor with the steel blade. Make sure that no large chunks are left (it holds together better as finer pieces). In a small bowl, stir together the melted butter, graham cracker crumbs and sugar. I used parchment paper to line an 8″x 8″ glass pan (you could put straight into pan) and firmly push the graham cracker mixture into the bottom evenly. Bake this for about 10 minutes, until the crust is dry and golden brown. Allow to cool completely on a wire rack. Keep the oven on.

  2. Make key lime filling: Prepare your limes. This could take a little while since they are quite small. Through my practice I found getting all the zest I needed first was best then moved onto juicing them. After zesting take a quick break to start the mixing of the yolks and zest (then juice while it’s mixing). In a stand mixer, whisk together the egg yolks and zest on high until very thick, about 5 minutes. Continue mixing but reduce speed to medium and in a slow steady stream add the condensed milk. Then raise the speed to high again and mix until thick, about 3 more minutes. After it thickens reduce speed to low and add the lime juice mixing until just combined.

  3. Bake the squares: Spread the filling in an even layer over the cooled crust. Bake in the 350 degrees F oven for 10 minutes, rotating halfway through. The filling will be just set. Remove and allow to cool completely on the wire rack.

  4. Refrigerate the squares and final touches: Refrigerate the cooled bars for at least 4 hours to allow the filling to fully set. Once set cut into squares (any size you like! or 2″x 2″ works well). Whisk the heavy cream in the stand mixer on medium high until stiff peaks form. Cut the remaining 2-3 limes in half and then into small slices. Garnish each square (or just some) with whipped cream and a key lime slice.

Recipe Notes

Recipe adapted from Martha Stewart.

If after finishing these you are in the mood for more lime desserts you could try these lime cookies!

  • Leanna K September 23, 2016 at 6:02 pm

    These look amazing! Can’t wait to give them a try:)

    • Brooke September 26, 2016 at 9:35 am

      Thanks Leanna! Hope they come out well – I love the tartness!