3 packages unflavored gelatin (I’ve still not found an acceptable vegan substitute)
Approx 1 1/2 c. granulated sugar
1 c. light corn syrup
1/4 c. cornstarch
1/4 t. salt
1 t. vanilla extract (Ms. Garten’s variation calls for 1 T. vanilla extract)
In a saucepan combine the remaining 1/2 c. water, granulated sugar, corn syrup and salt. Place over medium high heat, cover and cook for 3 to 4 minutes. Uncover, clip a candy thermometer (I always use my Thermapen) onto the side of the pan and continue to cook until the mixture reaches 240 degrees F, approx. 7 to 8 minutes. Once the mixture reaches 240 degrees F, immediately remove from heat.
Add the whisk attachment to your stand mixer. Turn the mixer on low speed and, while running, slowly pour the sugar syrup down the side of the bowl into the gelatin mixture. Once you have added all of the syrup, increase the speed to high. Continue to whip until the mixture becomes very thick and is lukewarm, approx. 12 to 15 min., but could take longer depending on your stand mixer’s abilities . Add the vanilla during the last minute of whipping. While the mixture is whipping, prepare the pan.
Combine the confectioners’ sugar and cornstarch in a small bowl. Lightly spray a 13 by 9-inch baking pan with nonstick cooking spray. Add the sugar and cornstarch mixture and move around to completely coat the bottom and sides of the pan. Doing this thoroughly is key to the marshmallows not sticking to the pan. Return the remaining mixture to the bowl for later use.When ready, pour the mixture into the prepared pan, using a lightly oiled spatula for spreading evenly into the pan. Dust the top with enough of the remaining sugar and cornstarch mixture to lightly cover. Reserve the rest for later. Allow the marshmallows to sit uncovered for at least 4 hours, up to overnight.
Turn the marshmallows out onto a cutting board and cut into 1-inch squares using a pizza wheel dusted with the confectioners’ sugar mixture. Once cut, lightly dust all sides of each marshmallow with the remaining mixture, using additional if necessary. Store in an airtight container for up to 3 weeks.
Source: http://www.foodnetwork.com/recipes/alton-brown/homemade-marshmallows-recipe.html (last accessed 1/3/2015).