Place water, sugar, and corn syrup in a medium saucepan. Stir to combine.
Insert a candy thermometer into the pot and heat over medium-high. Do not stir from this point on as crystals will form.
Ensure mixer bowl and whisk are completely grease free.**
Place egg whites and cream of tartar in the bowl of a stand mixer.
When the sugar syrup reaches about 225°F, start whipping the egg whites to soft peaks. Approx 3-4mins.
When the whites are ready, the sugar syrup should be at 240°F. Remove from the heat, turn mixer to medium and very slowly and carefully pour the sugar syrup into the whites in a thin, steady stream.***
Once all of the syrup is in, set mixer to medium/high and continue whipping. The whites will deflate at first, but they will thicken and fluff up.
Continue to whip for 7-8 minutes, or until the mixture is thick and glossy. Add in vanilla and whip until the fluff has cooled.