Caution: it is extremely hot. Using a freestanding mixer or electric whisk, whisk the egg whites in a large mixing bowl until stiff peaks form when the whisk is removed. Still whisking ...

Line a large baking tray with non-stick baking paper. In a very clean bowl, whisk the egg whites with an electric whisk on high speed and add 300g/10½oz of the sugar a spoonful at a time ...