Coat a 9x13 baking pan with cooking spray. Set aside.

In a large bowl, mix the gelatin and 1/2 cup of the cool water. Let stand until soaked.

While soaking, in a medium saucepan, mix together the rest of the cool water, granulated sugar, light corn syrup and salt and heat on medium until sugar is completely dissolved, about 5 minutes. Turn heat up to high and bring to a rapid boil for one minutes, without stirring. Mixture will foam and rise quickly and then fall and continue to simmer. Remove from the heat.

Slowly pour the warm sugar mixture into the large bowl of gelatin while beating on low with a hand mixer. Increase speed to high and whip mixture until light and fluffy, about 10 minutes. Add vanilla and beat to combine.

Using a greased rubber spatula, pour the mixture into the greased pan and spread out evenly. Sprinkle with 1/4 cup powdered sugar and place in the refrigerator for 3 hours or overnight before cutting.

Use a greased cookie cutter or knife to create shapes of marshmallows you desire.

Place cut out marshmallows in a large bowl and sprinkle with remaining powdered sugar to coat. Store in an air tight container at room temperature for up to 1 week or in the freezer for up to 3 months.