To make Italian meringue, it's important to cook the sugar to 121° C (250° F) or hard ball stage. Use a candy thermometer!

1. Cook the sugar to 121° C (250° F) or hard ball stage:
2. Dissolve 150 g (3/4 cup) sugar in 60 g (1/4 cup) water and cook until a candy thermometer reaches 121° C (250° F). At this temperature the cooked sugar syrup is thicker. Dip the tip of a soup spoon into the boiling syrup then immediately plunge it into cold water: the sugar should form a soft ball.
3. Using an electric mixer, beat the egg whites to soft peaks.
4. When the sugar syrup reaches 121° C, pour it into the egg whites while beating at low speed.
5. Increase the speed to high, and continue beating until the mixture has cooled completely.