Lightly butter and dust a 9" square baking pan with powdered sugar.

In a small bowl, mix the gelatin and 1/2 cup cold water together. Set aside for 10 minutes to thicken up.

Place the remaining 1 cup of water and sugar in a deep saucepan over medium heat. Stir until sugar is dissolved.

Use a candy thermometer to know when the sugar has reached 240F, then carefully remove and pour into your stand mixer fitted with the whisk attachment.

Add the gelatin mixture. Beat on LOW speed for 2 minutes, then increased speed to HIGH for 8-10 minutes, until doubled in volume and super fluffy. Add the vanilla and salt half way through whipping.

Pour into the prepared pan and smooth out with a spatula. Dust with more powdered sugar then set aside uncovered for 2-3 hours, until set. Slice into individual marshmallows to enjoy!