Butter's Famous Marshmallows

Ingredients:

1 cup water
2 tbsp unflavored gelatin 
2 cups sugar
1/2 cup light corn syrup 
1/2 tsp salt
2 tbsp vanilla (or other flavor)
about 2 cups icing sugar

Directions:

1. In a stand mixer fitted with a whisk attachment, pour in 1/2 cup of the water and sprinkle with the gelatin. set aside to allow the gelatin to soak in. 
2. In a medium saucepan over high heat, add the sugar, corn syrup, salt and remaining 1/2 cup of water. Bring to a rolling boil and continue to boil for 1 minute. Remove from the heat.
3. Turn the mixer to low and mix the gelatin once or twice to combine it with the water. Slowly add the hot sugar mixture, pouring it gently down the side of the bowl, and continue to mix on low.
4. Turn the mixer to high and continue to whip for 25-30 minutes until the marshmallow batter almost triples in size and becomes very thick. Scrape down the sides of the bowl frequently to avoid the batter overflowing as it grows. Stop the mixer, add the vanilla (or other flavors) and then whip briefly to combine.
5. Transfer the mixture to the prepared pan and use spatula or bench scraper to spread it evenly into the pan. Work quickly, as the marshmallow becomes more difficult to manipulate as it sets.
6. Grease a sheet of plastic wrap with cooking spray and lay it across the top of the marshmallow. Press down firmly on the plastic wrap, to seal it smoothly and tightly against the mixture.
7. Leave the marshmallow to set at room temperature for at least 3 hours or overnight. 
8. Sprinkle a work surface or cutting board with the icing sugar. Run a knife along the top edge of the pan to loosen the marshmallow slab. Flip the pan upside down onto the counter or board. Scoop up handfuls of icing sugar and rub it all over the marshmallow slab.
9. Use a large kitchen knife to cut the slab into 1 by 1 inch squares. Roll each square into the remaining icing sugar, coat completely.