Combine gelatin and half the water in a mixer bowl. Set aside and let the gelatin bloom.
Mix sugar, corn syrup, water, and salt in a saucepan. Over medium heat, cook till sugar is dissolved. Turn the heat up.
On high heat cook sugar mixture till firm ball stage or till 240 - 250 degrees F. Should form a firm ball when dripped in cold water, but still be able to squeeze it. Not rock hard.
Grease 9 x 13 pan with cooking spray.
Using whisk attachment on mixer, slowly add in hot sugar mixture and turn mixer to lower speed.
Increase speed to high and mix until marshmallow liquid is cooled down enough to touch. Mixture should be fluffy. Mix time is about 4 - 8 minutes.
Add in vanilla and peppermint extract. Mix in peppermint flakes.
If using food coloring, pour half of the marshmallow into the greased pan. Using a greased spatula, smooth and spread out the marshmallows quickly.
Use red food coloring in the rest of the marshmallow mixture. Pour red marshmallow on top of the white marshmallow. To make the coverage even, pour in 6 blobs across the pan. Use a knife or spatula to marble the marshmallow by dragging it through the white. If the marshmallow becomes unworkable, nuke in the microwave for 10 seconds.
Or you can just keep it plain white, which looks just as beautiful.
Let sit for 5 hours or overnight to cure.
Mix confectioners sugar and cornstarch.
Dust top of marshmallows and a cutting board with cornstarch mix.
Flip over the pan and let the marshmallow slab fall onto the cutting board.
Dust pizza cutter with powder and cut into squares. Or you could use cookie cutter shapes.