Using electric beaters, whisk 2 egg whites until frothy. Add 2 tbsp (30g) caster sugar and whisk to soft peaks. Combine ⅔c (150g) caster sugar with 100ml water in a saucepan over low heat, stirring until sugar dissolves. Increase heat to medium and simmer for 2 mins or until mixture reaches 115°c on a sugar thermometer. Whisking constantly, gradually pour sugar syrup into egg white mixture in a thin, steady stream, whisking until mixture is thick, glossy and cold.