Separate your eggs, and place the whites into a clean bowl. Save the yolks for another recipe.
In a saucepan larger than you think you will need - this expands as it boils up - add the sugar, corn syrup, and water. Turn the heat to medium and gently swirl the pan every 30 seconds or so to mix the ingredients together. Use a pastry brush to wash the sides with water to ensure no sugar crystals are adhering to the side of your pan.
3/4 cup sugar, 1/2 cup corn syrup, 1/4 cup water
While your sugar is cooking, beat your egg whites to a soft peak, no more. This will take just a couple minutes, so watch them. Once they're done, they can rest for the few minutes the sugar mixture will take to finish.
3 egg whites
Bring the sugar mixture to a boil, and add your candy thermometer. Cook to 240 degrees.
Once the sugar mixture is at 240 degrees, remove it immediately from the heat. Turn your mixer on low and add just a dribble of the sugar mixture to your eggs to temper them. You want to heat them slowly so that they incorporate the mixture without scrambling. Do this two to three times, then pour all the sugar mixture in slowly while beating.
Once the sugar syrup is all added, turn your mixer to medium. Add the salt and vanilla, and turn the mixer to high. Beat for 5 or so minutes, until the fluff has gotten thick and glossy.