Die, Jet-pufffed, die.

Ingredients
3 envelopes of Knox gelatin (2-1/2 to 3 Tablespoons)
1 cup cold water (1/2 cup at a time)
1-1/2 cups granulated sugar
1 cup light corn syrup
1/4 teaspoon salt
1 tablespoon vanilla extract
powdered sugar (about 1/2 cup)

Coat an 8x8-inch (or 9x9-inch) non-stick pan with cooking spray and then liberally “flour” with some of the powdered sugar

Mix gelatin with 1/2 cup water In the bowl of an electric mixer.  Set aside for up to 25 minutes while you do the rest of the process.  It will begin to set up.

Combine sugar, corn syrup, salt and remaining 1/2 cup water in a medium saucepan.  Bring to a rolling boil and then maintain a low boil until a candy thermometer reads 244-degrees F.

Carefully pour the hot sugar mixture into the mixer on its slow setting.  Then bring up the mixer up to high speed and mix/beat for 15 minutes.  Mixture will triple in volume.  Add a liberal Tablespoon of vanilla extract.  (Bakerina recomments adding an equal measure of espresso powder for a magically buttery marshmallow). 

Pour the mixture into the pan.  Let cool/set uncovered for at least 8 hours.  Powder the top with sugar, loosen the sides with a knife and release to a cutting board covered in powdered sugar.  Using a long knive lightly poswered in poswered sugar, slice into cubes—slicing straight down, don’t saw back and forth.  Roll each marshmallow in powdered sugar to coat.