How to Make It
Spray a 9-by-13-by-1-inch baking pan with cooking spray or lightly brush with canola oil.
In a standing electric mixer fitted with the whisk, add 6 ounces of cold water; sprinkle with the gelatin and let stand.
In a small saucepan, combine the sugar, corn syrup, honey, salt and 4 ounces of water. Cook over low heat, stirring occasionally, until the sugar is dissolved. Attach a candy thermometer to the side of the pan and bring the mixture to a boil without stirring. Boil, brushing down the sides of the pan with a wet pastry brush, until the thermometer registers 250°.
With the stand mixer on low speed, slowly pour in the hot sugar mixture. Once all of the sugar mixture is added, increase the speed to high and beat until thick and glossy, about 10 minutes. If using the powdered fruit, add half of it to the mixture and beat until well combined.
Transfer the marshmallow to the prepared pan and use a lightly greased offset spatula to spread it in an even layer. Spray the top of the marshmallow with cooking spray and cover with a piece of parchment paper until set and firm, about 3 hours.
In a medium bowl, whisk the confectioners’ sugar with the cornstarch and remaining powdered fruit, if using. Invert the marshmallow onto a cutting board dusted with confectioners’ sugar. Using a lightly greased knife, cut the marshmallow into 1 1/2- to 2-inch squares. Toss the marshmallows in the confectioners’ sugar mixture. Store the marshmallows in an airtight container for up to 2 weeks.