1. In the large bowl of a stand mixer fitted with the whisk attachment, mix gelatin and ½ cup of the cold water just until combined.
2. In a small saucepan with candy thermometer attached, combine remaining ½ cup water, sugar, corn syrup, and salt. Heat over medium heat until mixture reaches 240°F (soft ball stage).
3. Remove from heat. Turn mixer on low speed and very gradually drizzle sugar mixture into bowl with gelatin. Raise speed to high and mix until very, very thick and lukewarm. This will take about 15 minutes. Add extract and food coloring, then mix again until thoroughly combined.
4. In a small bowl, whisk together the confectioners’ sugar and cornstarch. Spray a 9x13-inch baking pan with cooking spray. Dust pan generously with cornstarch mixture. Set remaining mixture aside to use later.
5. Spray a silicone spatula with cooking spray and spread marshmallow mixture into pan. Dust top of marshmallow mixture with some more of the cornstarch mixture. (You should still have some cornstarch mixture leftover at this point. Do not discard it.)
6. Let marshmallow mixture set at room temperature, uncovered, for 8-24 hours. Overnight works great.
7. Once marshmallow has set, turn pan over onto a cutting board to remove the marshmallow. It should come out easily. Using a knife or cookie cutters, cut marshmallows into the size and shape you desire, dusting the cut sides with remaining cornstarch mixture.
8. Store in airtight container at room temperature.

To dip marshmallows in chocolate:

1. Heat chocolate and butter in a double boiler (or in the microwave for about 45 seconds), stirring frequently. Dip marshmallows in melted chocolate and arrange on waxed paper to cool. Decorate with sprinkles while chocolate is still warm, if desired.