In a medium saucepan, combine the remaining 1/2 cup of water, granulated sugar, and salt. Place the saucepan over medium-high heat and stir gently until the sugar has completely dissolved.
Continue cooking the syrup until it reaches a temperature between 242°F / 116°C and 245°F / 118°C. Use a candy thermometer to monitor the temperature closely.
Increase the speed of the mixer to high and add the vanilla and salt. Continue whisking for about 7-10 minutes or until the mixture becomes thick, glossy, and triples in volume.
Dust a surface with a mixture of powdered sugar and either cornflour or arrowroot flour. Toss each piece in the powdered sugar mixture to ensure all sides are coated.