Yield: 25 marshmallows
Active Time: 25 minutes
Total Time: 1 day
1/2 cup powdered sugar
1/2 cup cornstarch
5 teaspoons grass-fed gelatin
1/2 cup plus 3 tablespoons water, divided
2 cups sugar, divided
3/4 cups light corn syrup
6 egg whites
1/4 teaspoon lemon juice
1/8 teaspoon salt
1 teaspoon vanilla extract
Sprinkle gelatin over 1/2 cup water in a microwave-safe bowl. Set aside.
Bring 1 1/2 cups sugar, corn syrup, and 3 tablespoons water to a boil over low heat.
Place egg whites, lemon juice, and salt in bowl of stand mixer fitted with whisk attachment and beat on medium-high until soft peaks form. Gradually add remaining 1/2 cup sugar with mixer on high. Return speed to medium and very gently, taking care not to splash, pour hot sugar syrup into egg whites with mixer running. Turn back up to high and beat for 5 minutes. Microwave gelatin mixture for 15 seconds, then pour into running mixer. Beat in vanilla extract.
Scrape marshmallow mixture into prepared pan and spread evenly. Allow to dry overnight uncovered.
Dust another 1/4 cup sugar-cornstarch mix onto clean surface, and flip marshmallows out onto it. Cut into desired shapes and roll sticky cut sides in remaining 1/4 cup mix. Store in an airtight container.