In your stand mixer add 1/2 cup of water and vanilla extract and sprinkle in gelatin powder. This will bloom while you're working on your sugar mixture. Also, I use my whisk attachment for whipping marshmallows.
In your large saucepan add the other 1/2 cup of water, sugar, corn syrup and salt. Over low heat stir until sugar is dissolved then increase to a medium heat and boil mixture until your candy thermometer reaches 240 degrees F.
Remove from heat and slowly pour your sugar mixture into your gelatin bloom while your mixer is running on low. Turn speed up to high and whip until thick, white and almost tripled in volume. When strings start pulling from the sides it's ready.
Pour the marshmallow mixture into your greased pan. Cover and let set for at least 4 hours or overnight.
Now that your marshmallows are set up make your dusting powder to coat your marshmallows and to use while you're cutting them.
Sprinkle a cutting board with the cornstarch powdered sugar mixture. I also find oiling my work surface helps the marshmallows not stick. If you need to run a thin knife or spatula around the edges to remove from the pan. Flip and slowly ease your marshmallow onto the cutting board.
Sprinkle more of your dusting mixture on top and using an oiled knife cut into squares. Then roll each square in the dusting mixture and shake the excess off and store. I like to shake in an extra fine metal mesh sieve to get the most excess off. Store in an airtight container at room temperature. Enjoy in hot chocolate or just snacking.
