Prepare the Pan:

1. Line the Pan:
   Line an 8×8-inch pan with parchment paper, leaving overhang on the sides for easy removal. Lightly grease the parchment paper with non-stick spray or a small amount of oil.

Bloom the Gelatin:
2. Bloom the Gelatin:
In the bowl of a stand mixer, combine the 1/4 cup cold water and the gelatin. Let sit for 5 minutes to bloom.

Cook the Syrup:
3. Make the Syrup:
In a small saucepan, combine the granulated sugar, corn syrup, water, and raspberry puree.
Heat over medium heat, stirring until the sugar dissolves.
Stop stirring, increase the heat, and bring the mixture to a boil. Heat until the syrup reaches 240°F (soft ball stage) on a candy thermometer.

Combine Syrup and Gelatin:
4. Pour Syrup into Gelatin:
With the mixer on low speed, carefully pour the hot syrup into the bloomed gelatin. Be cautious, as the syrup will be very hot.

Whip the Mixture:
5. Whip:
Increase the mixer speed to high and whip for 8-10 minutes, or until the mixture is thick, glossy, and fluffy.
Add the salt, vanilla extract, raspberry extract, and food coloring (if desired) in the last minute of whipping.

Spread into the Pan:
6. Pour and Set:
Pour the marshmallow mixture into the prepared pan and spread it evenly using a greased spatula.
Allow the marshmallows to set at room temperature for 6-8 hours or overnight.

Cut and Coat:
7. Cut and Coat:
In a small bowl, mix the powdered sugar and cornstarch.
Dust a clean surface with some of the mixture.
Lift the marshmallow block out of the pan and invert it onto the dusted surface.
Cut into squares or desired shapes using a greased knife or cookie cutter.
Toss each piece in the powdered sugar mixture to coat.