Prepare the pan: Line a 9×9-inch (23×23 cm) baking pan with parchment paper and lightly grease it.

Bloom the gelatin: In a stand mixer bowl, combine 1/2 cup of cold water with gelatin and let sit for 5–10 minutes.

Cook the sugar syrup: In a saucepan, mix granulated sugar, corn syrup, salt, and remaining 1/4 cup water. Heat on medium, stir until sugar dissolves, then increase to medium-high and cook until mixture reaches 240°F (115°C).

Whip the marshmallow mixture: With the mixer on low, slowly pour the hot syrup into the bloomed gelatin. Gradually increase to high speed and beat for 10–12 minutes, until thick and fluffy.

Flavor and color: Add cotton candy flavoring and a few drops of gel food coloring. Mix until evenly combined.

Transfer to pan: Pour the mixture into the prepared pan and smooth the top with a greased spatula. Let it set at room temperature for 6–8 hours or overnight.

Cut and coat: Mix powdered sugar and cornstarch in a bowl. Dust a surface with it, turn out the marshmallows, remove parchment, and dust the top. Cut into shapes using a greased knife or cutters and toss to coat.

Serve: Store in an airtight container at room temperature for up to 1 week.