Bloom the gelatin in the bowl of a stand mixer by whisking the gelatin and half of the water. Let stand for 8-10 minutes.
2½ tablespoons powdered gelatin, 1 cup cold water
While the gelatin is blooming, whisk the remaining water, sugar, corn syrup and salt together in a medium saucepan set over medium heat. Allow to simmer for 6-8 minutes, whisking constantly. The mixture will start to become clear. Remove from the heat.
1½ cups granulated sugar, ¾ cup light corn syrup, ½ teaspoon kosher salt
Using a whisk attachment, turn the mixer to low speed and slowly pour in the sugar mixture. Once incorporated, continue to whisk for another minute. Increase speed to high for 10 minutes or until a fluffy, white, marshmallow mixture has formed.
Add in the cotton candy flavoring and whisk for another minute. Divide marshmallow mixture into two separate bowls. Color each of them pink and blue.
2 teaspoons cotton candy flavoring, Pink and blue food coloring
Dust a 9x13-inch pan with powdered sugar to prevent the marshmallows from sticking. Spoon the marshmallow into the pan in alternating colors. Using a rubber spatula, smooth the top. Dust with the remaining powdered sugar. Cover with plastic wrap and let set for 8-12 hours.
¾ cup powdered sugar
Once set, remove the marshmallow slab from the pan and place it onto a cutting board. Dust off any excess powdered sugar. Cut the marshmallows into 1-inch squares. Serve and enjoy!