key lime pie marshmallows

When I first made homemade marshmallows, I was blown away. I thought I was doomed to an eternity of eating marshmallows of the storebought, chemical-filled Jet Puffed variety. I will use these in a pinch, like in my rocky road squares, but I much prefer the homemade kind. They’re surprisingly simple, too!


I had been kicking around the idea of key lime pie flavored marshmallows for a while, and I finally got around to creating them. They are just as I hoped they’d be: soft and pillowy, chewy and bright with lime juice, with the perfect touch of vanilla to mimic fluffy piles of sweet whipped cream on a slice of key lime pie. Give these a shot if you’re looking for a humble little sweet treat to perk up your day!

key lime pie marshmallows

(yields 48 little marshmallow squares)

for lime layer

11 grams (1 1/2 packets) powdered gelatin

1/4 cup cold water

1/4 cup key lime juice (regular lime juice works just fine)

6 oz (3/4 cup) granulated sugar

5.5 oz (1/2 cup) corn syrup

pinch of salt

a few drops lime oil

a drop or two of green food coloring, optional

for vanilla layer

11 grams (1 1/2 packets) powdered gelatin

1/2 cup cold water, divided

6 oz (3/4 cup) granulated sugar

5.5 oz (1/2 cup) corn syrup

pinch of salt

3/4 teaspoon vanilla extract or vanilla bean paste

to line the pan

1 sleeve (9 whole crackers) honey graham crackers, crushed fine

Spray a 9″x13″ baking dish or a 1/4 sheet pan [edit: I’d actually recommend using an 8×8 inch square baking dish cause you’ll end up with a thicker, more appealing-looking marshmallow!] with cooking spray. You can crush your graham crackers in a food processor if you have one, but I find the easiest way is to just put all the crackers into a Ziploc bag and crush them with a rolling pin. Once one side is all crushed, flip the bag over and go over the crumbs once more. Sprinkle 1/3 cup of the crushed grahams into the greased pan. Shake around the pan to evenly coat the bottom, and set aside.

To start the lime layer, bloom the gelatin: Pour 1/4 cup of lime juice into the bowl of a stand mixer. Sprinkle on the gelatin and stir by hand with the whisk attachment, and set aside while you cook the sugar syrup.

CrumbsBloomingSugar Syrup

In a small saucepan on medium-low heat, cook the 1/4 cup of water, sugar, corn syrup and salt without stirring, until a thermometer placed in the syrup reads 240 degrees (soft ball stage). This took about 12-14 minutes for me, but it’ll depend on your stove.

Once the syrup reaches 240, immediately take off the heat and turn on the mixer with the whip attachment in place. Slowly pour the super hot syrup down the side of the bowl into the gelatin mixture, while the mixer is running on low. Once all the syrup is in the bowl, add the lime oil and the green coloring and crank the mixer up to high speed and let it whip up the marshmallow for about 3-4 minutes. The marshmallow will still be quite runny at this point. With an oiled spatula, scrape out the lime marshmallow into the crumb-lined pan and gently spread it out to the edges.  Don’t worry too much if it’s not completely flat. Be careful about using too much oil on the spatula, if the top of the lime layer is too greasy, the vanilla layer won’t adhere to it. Set the pan aside while you make the vanilla layer. Wash out the mixer bowl, whip attachment and spatula to get them ready for the vanilla layer. There’s no need to wash out the syrup pan, just proceed with the next layer.

Whip1  Whip2

Lime Layer

For the vanilla layer, repeat the steps for making the lime layer, except use 1/4 cup of cold water in place of the lime juice for blooming the gelatin, and 1/4 cup water in the sugar syrup. Once the syrup comes off the heat, add it to the bloomed gelatin just as you did for the lime layer, and add the vanilla extract before turning the mixer to high. Beat on high for 3 to 4 minutes and scrape out the vanilla marshmallow with an oiled spatula and pour it evenly on the lime layer. Spread it carefully to cover the surface of the lime layer. Sprinkle on 1/3 cup more of the graham cracker crumbs, saving the excess crumbs to roll the marshmallows in later. Set the pan aside, loosely covered with plastic wrap, at room temperature for several hours or overnight.

Spread1 Layered2 Layered

Once the marshmallow is set, carefully lift it out of the pan and onto a cutting board. Place your remaining graham cracker crumbs into a large bowl. Any excess crumbs left in the pan can be added to the bowl of crumbs. With a sharp knife, slice the marshmallow vertically in half, and then cut each half into 2, so you’ve got 4 equal pieces. Cut those 4 pieces in half so you have a total of 8 strips of marshmallow. Turn the cutting board 90 degrees and cut the marshmallows in half, and then each half into thirds, so you have a total of 48 marshmallow squares (6 on the short side and 8 on the long side).

Cut1 Cut2 Cut3 Cut4

When they’re all cut, drop a few squares at a time into the bowl of crumbs, and toss to coat the cut edges. Eat one immediately while they’re fresh, and savor all the lime-y goodness!


These marshmallows are refreshing, light and airy, full of lime and vanilla flavors, and perfect for when you want a quick sweet snack. They’ll keep well in a Ziploc bag at room temperature for a week or so, though they do get a little chewier as time goes by.





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