Grease a 9x9-inch baking pan with cooking spray and set aside.

In the bowl of a stand mixer, add ⅔ cup cold water. Sprinkle gelatin on top and let bloom.

In a medium saucepan over medium-high heat, combine granulated sugar, corn syrup and ⅔ cup water. Stir until sugar is dissolved. Bring the mixture to a boil, swirling the pan occasionally, until the mixture reaches exactly 240°F on a candy thermometer, about 10-12 minutes. Immediately remove from heat.

With the stand mixer on low speed, slowly and carefully pour the melted sugar mixture into the gelatin mixture. Add the peppermint extract and salt.

Slowly (to avoid splashes) increase the speed to high and whip until the mixture is stiff and white, about 10-12 minutes. When you remove the whisk, stiff peaks should form that take a few seconds until they fall back into the marshmallow mixture. Working quickly, pour the mixture into the prepared baking pan and use a spatula to help spread evenly.

While the marshmallows are warm, add droplets of red food coloring to the top. Use a toothpick or skewer to swirl the food coloring throughout the marshmallows.

Let the marshmallows sit and firm for at least 4 hours at room temperature or 2 hours in the refrigerator.

Dust your work surface with powdered sugar or cornstarch. Use a butter knife to slice around the edges of the pan, then turn the marshmallow out onto the work surface. You may need to pry it out at a corner. Use a sharp knife to cut the marshmallow into (at least) 16 pieces. If needed, spray the knife with cooking spray to help prevent sticking. If there is excess cooking spray on your marshmallow, dab with a paper towel to remove.

Roll each marshmallow in powdered sugar or cornstarch on each side to prevent sticking, then serve.