- 41/2 tsp unflavored gelatin
- 1/4 cup freshly squeezed key lime juice
- 1/4 cup cold water
- 1 cup sugar
- 1/2 cup light corn syrup
- 1/4 cup water
- 1/8 tsp salt
- 1 tsp pure vanilla extract
- green gel food coloring
- 1 cup graham cracker crumbs* (about 8 store-bought cracker sheets)
- 3/4 cup confectioners' sugar
- 1/2 cup cornstarch or potato starch
*For a great textural element, pulse the crackers in a food processor to get nubbly, not-too-finely ground crumbs. Or forgo altogether in favor of 1/2 cup Classic Coating, whisked with a few packets of True Lime powder (found by the drink mixes in supermarkets).
Classic Coating: Sift the ingredients together in a large bowl or combine them in a food processor. I tend to make several cups’ worth at a time and store it in an airtight container; it keeps forever.
Lightly coat an 8-by-8-inch baking pan with cooking spray.
Whisk together the gelatin, key lime juice, and cold water in a small bowl. Let it soften for 5 minutes.
Stir together the sugar, 1/4 cup of the corn syrup, water, and salt in a medium saucepan over high heat. Boil, stirring occasionally, until the temperature reaches 240°F. Meanwhile, pour the remaining 1/4 cup corn syrup into the bowl of an electric mixer fitted with the whisk attachment. Microwave the gelatin on high until completely melted, about 30 seconds, and pour it into the corn syrup. Set the mixer to low and keep it running.
When the syrup reaches 240°F, slowly pour it into the mixer bowl. Increase the speed to medium and beat for 5 minutes. Increase the speed to medium-high and beat for 5 more minutes. Increase to the highest setting, add the vanilla and food coloring, and beat for 1 minute more. The finished marshmallow will be tripled in volume. Pour it into the prepared pan, using an offset spatula to smooth it into the corners. Sprinkle graham cracker crumbs evenly over top. Let it set for 6 hours in a cool, dry place.
Use a knife to loosen the marshmallow from the edges of the pan and invert the slab onto a work surface. Sprinkle with graham cracker crumbs. Cut it into pieces and dip the sticky edges in more crumbs, patting off the excess.
Recipe courtesy of Marshmallow Madness!: Dozens of Puffalicious Recipes by Shauna Sever/Quirk Books, 2012.