put the gelatine in the bowl of a stand mixer

pour 2 TBSP cold water over it and let it sit while you work on the sugar and corn syrup

bring the remaining water, sugar, corn syrup, and pinch of salt to a boil and boil until it hits the soft ball stage, 240˚, stirring occasionally

remove from the heat and let it rest a moment

fit the mixer with the whisk attachment and stir the gelatine and water mixture on low

pour the boiling sugar mixture over the gelatine very slowly, don't add it all at once, and be sure to keep the mixer on the lowest setting

once you've poured all the sugar in turn up the mixer one notch

set a time for 10 minutes and every minute or so turn up the mixer a notch until you're beating it on high

while the mixture is beating you can prep the pan by lightly greasing it and lining it with parchment paper, then lightly grease again, then dust it with powdered sugar

also gently warm about 1/2 cup of the Nutella while the mixture is beating

once you hit 10-11 minutes of mixing you should have a huge fluffy blob in the mixer

if you don't continue beating the mixture 1-2 more minutes

once you have a huge white fluffy blob turn the mixer down to low and add the vanilla and the warmed Nutella

whip again until fully incorporated

pour into the prepared pan

immediately scoop the last of Nutella on top of the marshmallow

use a butter knife to swirl

let rest 8 hours or more

dust the top with more powdered sugar

use a knife dusted with powdered sugar to cut them

dust all the sides with powdered sugar

store where it's dry, and only lightly cover them

or store open in a secure cupboard to dry enough for s'mores or cocoa