Tips

— Use a spotlessly clean bowl, and make sure the whisk is clean, too. Copper and silver bowls block sulphur reactions between proteins and help create a more stable froth. Glass and metal bowls work well, too, though plastic is harder to get spotlessly clean as it is porous.

— Be careful not to let any egg yolk get into the whites, as the fat will stop the eggs from foaming.

— Once your egg whites are whisked, fold them into the cake mixture gently with a large metal spoon, to avoid losing any of the volume.