Get your gelatin set up with half the water in a stand mixer
Put the rest of the water, corn syrup, sugar and salt in a saucepan over medium-high heat.
Cover and let cook for 4 minutes.
Cook sugar mixture to 240F and immediately remove from heat.
Get your mixer going on the lowest speed.
Drizzle sugar mixture down side of bowl. Do not get on the beater or on your hand unless you want a trip to the burn unit.
Turn mixer to high and go get your pan ready. You have roughly 10 minutes. Check mixer occasionally to make sure it's not walking or smoking. The mixture is thick and can blow out a crappy mixer.
Mix powdered sugar and cornstarch. If you don't have cornstarch, just use straight up powdered sugar.
Spray cooking spray on a 13x9 pan (for big marshmallows) or sheet pan. Coat with some of the powdered sugar mixture.
After a few minutes.
Getting closer. At about the 9 minute mark, add the vanilla. I added a dash of peppermint extract too.
This is what you want to see. Thick and lukewarm.
Spread goop in pan.
Cover top with more powdered sugar mixture. Let sit at least 8 hours (I do overnight). Do not cover.
Turn out marshmallows and cut up with oiled knife or pizza cutter.
Toss in remaining powdered sugar mixture and put in airtight containers.
Or, use a sprayed cookie cutter for fancy shapes.
Tada! Now go make some cocoa and enjoy.