Preparation Steps

• Grease a 9x13 inch baking pan and line it with parchment paper, leaving an overhang on the sides. Dust the parchment paper with some of the powdered sugar and cornstarch mixture.
• In the bowl of a stand mixer, sprinkle the gelatin over 0.5 cup of water. Let it bloom for about 10 minutes.
• In a medium saucepan, combine the granulated sugar, corn syrup, 0.25 cup water, and salt. Stir to combine.
• Heat the sugar mixture over medium heat, stirring constantly, until the sugar dissolves. Bring to a boil and cook, without stirring, until it reaches 240°F (115°C) on a candy thermometer.
• Carefully pour the hot sugar syrup into the bloomed gelatin mixture. With the whisk attachment, beat on low speed until combined, then increase to high speed and beat for 12-15 minutes, or until the mixture is thick, glossy, and has almost tripled in volume.
• Beat in the vanilla extract.
• Pour the marshmallow mixture into the prepared pan and spread evenly. Sprinkle the remaining powdered sugar and cornstarch mixture over the top.
• Let the marshmallows set at room temperature for at least 4 hours, or preferably overnight.
• Once set, use the parchment paper overhang to lift the marshmallow slab out of the pan. Cut into squares using a pizza cutter or knife lightly coated with cooking spray or dusted with the sugar mixture.
• Dust the cut marshmallows with more of the sugar mixture to prevent sticking.