GRAHAM CRACKER CRUST

1. Adjust an oven rack to the middle position and heat the oven to 325 degrees. Pulse the whole graham crackers in a food processor until the crackers are broken down into coarse crumbs, about eight to ten 1-second pulses. Open and stir edges to make sure no large pieces are stuck and then repeat to make fine crumbs, another 8 to 10 times.
2. Transfer the crumbs to a medium bowl or large bowl and stir in the sugar to combine; add the melted butter and toss with a fork until the crumbs are evenly moistened.
3. Use the bottom of a 1/2 cup measuring cup to press the crumbs evenly into the bottom and up the sides of a tart pan with a removable bottom, forming a crust.
4. Bake the crust until deep golden brown and fragrant, about 15 minutes. Cool the crust on a wire rack while making the filling. When cool to the touch, you can refrigerate it (covered) until you are ready to fill it.

FOR KEY LIME CURD

1. Using the same large bowl from the crust – no need to clean the bowl – whisk together the sweetened condensed milk, flour, cream of tartar, and salt.
2. Then whisk in the egg yolks, whisking until no streaks from the eggs or flour remain. Continue to whisk in the lime zest and the lime juice.
3. Pour the mixture into a round bottomed sauce pan, and turn the stove on to medium heat. Stirring constantly, heat the mixture until it registers 160 degrees and thickens. This will ensure that the eggs are cooked through.
4. Turn off the heat, and add in the butter, one tablespoon at a time, whisking constantly until each one melts before adding the other.
5. Pour the lime curd on top of the still cooled graham cracker crust. Spread the curd evenly if needed with the back of a spoon.

MARSHMALLOW FLUFF

1. Place room temperature egg whites, sugar, and cream of tartar in a heatproof bowl – or I use the metal bowl from my stand mixer. Set bowl over a saucepan filled with two inches of simmering water creating a mock-double boiler. Do not let it touch the water.
2. Whisk constantly until sugar is dissolved and mixture has thinned out, about 6 minutes. The mixture will be thick at first, then thin out and appear frothy on top because of the air that you have added to the egg whites.
3. Using an instant read thermometer the temperature should read 160°F (71°C) to ensure that the egg whites are cooked through. It may take longer than 6 minutes, depending on how fast the water in your double boiler is boiling underneath. Adjust the heat on the water as necessary.
4. Remove from heat. (No need to let it cool down before continuing.) Add the vanilla extract and salt, then using a handheld or stand mixer fitted with a whisk attachment, beat on high speed until stiff glossy peaks form, about 5 to 8 minutes. The sides of the bowl will be cool and the marshmallow fluff will be cool and glossy.
5. Meringue can be spread, piped, or swirled onto cakes, cupcakes, and other confections. Serve immediately OR torch it with a kitchen torch for a delicious toasted marshmallow topping. (Do not place in the oven under the broiler—it will melt the marshmallows and the curd.)
6. If you’re feeling super fancy you can top the marshmallow fluff with toasted shredded coconut as well and extra lime slices.