https://www.foodnetwork.com/recipes/alton-brown/homemade-marshmallows-recipe-1953933

3 Packages / 3 oz Unflavored Gelatin
1 C Ice Cold Water
12 oz / 1 1/2 C Granulated Sugar
1 C light Corn Syrup
1/4 tsp Kosher Salt
1 tsp Vanilla Extract
1/4 C Confectioners' Sugar
1/4 C Cornstarch
Nonstick Spray/Oil

3 Packages / 3 oz Unflavored Gelatin 1 C Ice Cold Water 12 oz / 1 1/2 C Granulated Sugar 1 C light Corn Syrup 1/4 tsp Kosher Salt 1 tsp Vanilla Extract 1/4 C Confectioners' Sugar 1/4 C Cornstarch

1. Put the gelatin and 1/2 C water in the bowl of a stand mixer with the whisk attachment.
2. In a small saucepan combine 1/2 C water, the granulated sugar, the cornstarch, and the salt. Place over medium-high heat, cover, and cook for 3-4 minutes. Uncover. Cook until it reaches 240 degrees F (use a candy thermometer here). Immediately remove from heat.
3. Turn the mixer onto low speed and slowly add in sugar syrup to the gelatin mixture until all the syrup has been added. Increase the speed to high. Whip until the mixture becomes lukewarm, about 12-15 minutes. Add vanilla extract during the last minute.
4. While mixture is being whipped, prepare the pan. Combine the confectioners' sugar and the cornstarch in a small bowl. Lightly spray or use a paper towel with oil to lightly coat a 13x9 in pan. Sift the sugar-cornstarch mixture onto the pan, covering the inside of the pan. Set remaining mixture aside for later use.
5. Using a lightly oiled spatula, evenly spread the marshmallow mixture into the pan. Sift the sugar-cornstarch mixture over the mixture, lightly covering it. Let it sit uncovered for at least 4 hours up to overnight.
6. Turn the marshmallows out onto a cutting board and cut into desired shapes. Roll cut marshmallows in sugar-cornstarch mixture to cover all stickiness.
Store in an airtight container for up to 3 weeks.