Brush a 9-by-13-inch glass baking dish with oil. Line with parchment, allowing a 2-inch overhang on the long sides. Brush parchment with oil; set aside.
Pour ¾ cup of water into a saucepan, add sugar and stir until dissolved. Bring to boil and boil for 11 minutes (softball stage, 235*F. on the candy thermometer); Remove from the heat.
Meanwhile, put the other ¾ cup cold water into the bowl of an electric mixer; sprinkle with gelatin. Let soften 5 minutes.
After you have the sugar syrup at softball stage, stir it into the soaked gelatin. Add the vanilla and salt; let stand till partially cooled about 10 minutes.
Beat on high with the balloon whisk attachment for about 12 minutes or until mixture is fluffy white and fully thickened.
Pour into your prepared pan; smooth out the top. (You might want to spray a little nonstick spray onto a rubber spatula to help with this process.)
Set aside, uncovered, until firm, about 3 hours.
Once set, turn out and cut into squares. (I like to oil my knife or cookie cutter to do this, as it helps to cut a little easier. I've also found that using an oiled pizza cutter helps this go a little faster.)
Roll squares in powdered sugar. Store in an airtight container until ready to use.