In a mixing bowl, combine 1/2 cup cold water and gelatin. Let it sit to bloom.
In a saucepan, combine granulated sugar, corn syrup, salt, and the remaining 1/2 cup of water.
Heat the mixture over medium heat, stirring until the sugar dissolves.
Bring the mixture to a boil without stirring. Use a candy thermometer and cook until it reaches 240°F.
Remove from heat and let it cool slightly.
With a mixer on low speed, slowly pour the sugar mixture over the bloomed gelatin.
Increase the mixer speed to high and beat for about 10 minutes until thick and fluffy.
Add vanilla extract and mix for an additional minute.
Pour the mixture into a greased 9x13 inch pan, smoothing the top.
Dust with powdered sugar and let it set for at least 4 hours or overnight.