Add 1/2 cup cold water to the gelatin in a heat resistant, high walled mixing bowl.

In a saucepan, combine remaining 1/4 cup water, sugar, and corn syrup. Cook on medium high until mixture reaches 250 F.

With the mixer on low, slowly pour the syrup onto the gelatin. Add the salt and increase the speed to high. Continue to whip 13-15 minutes (the longer, the fluffier). Add the vanilla during the last minute of whipping.

While the mixture is whipping, combine powdered sugar and corn starch in a small bowl.

Lightly grease a 9 x 13 baking sheet with butter or vegetable oil, then coat with powdered sugar and cornstarch mixture.

When ready, pour the marshmallow mix into the baking sheet. Using a lightly oiled spatula, spread the marshmallow evenly.

Dust the top with the sugar mixture to lightly cover. Let marshmallows rest, uncovered, for at least 4 hours but up to overnight.

Transfer marshmallow to a cutting board and cut into squares using a knife or pizza cutter dusted with the sugar mixture. Lightly coat edges of squares with sugar mixture.

Enjoy right away, or store in an airtight container for up to 3 weeks.