4½ teaspoons unflavored powdered gelatin
½ cup cold water
¾ cup sugar
½ cup light corn syrup, divided
¼ cup water
2 teaspoons pure vanilla extract
½ cup Classic Coating plus more for dusting
1½ cups confectioners' sugar
1 cup cornstarch or potato starch
Lightly coat an 8-by-8-inch baking pan with cooking spray.
Whisk together the gelatin and cold water in a small bowl and let soften for 5 minutes.
Stir together the sugar, ¼ cup corn syrup, water and salt in a medium saucepan over high heat. Boil, stirring occasionally, until the temperature reaches 240 degrees.
Meanwhile, pour remaining ¼ cup corn syrup into the bowl of an electric mixer fitted with the whisk attachment. Microwave gelatin on high until completely melted, about 30 seconds. Pour it into the mixer bowl. Set the mixer speed to low and keep it running.
When the syrup reaches 240 degrees, slowly pour it into the mixer bowl. Increase the speed to medium and beat 5 minutes. Increase to medium-high and beat 5 more minutes. Beat on the highest setting for 1 to 2 minutes more and beat in the vanilla; the finished marshmallow will be opaque white, fluffy, and tripled in volume. Pour it into the prepared pan, using an offset spatula to smooth it into the corners.
For the coating: Sift the ingredients together in a large bowl or combine them in a food processor. This makes several cups; stored in an airtight container it keeps forever.
Sift coating evenly and generously over top. Let set for at least 6 hours in a cool, dry place.
Use a knife to loosen the marshmallow from the edges of the pan. Invert the slab onto a coating-dusted work surface and dust it with more coating. Cut into whatever size pieces you wish (a pizza cutter works great for squares). Dip the sticky edges of the marshmallows in more coating, patting off the excess.
Makes about 2 dozen 1½-inch mallows.
Variation: Super vanilla-ize these mallows by adding a scraped vanilla bean or dab of pure vanilla bean paste along with the vanilla extract.
"Marshmallow Madness!" by Shauna Sever (2012 Quirk Books)