Method:

• Put the egg whites, sugar and salt into a scalded mixing bowl.
• Using a whisk on the machine, blend ingredients together.
• Whisk for 2 minutes on top speed and then scrape down the sides of the bowl, whisk for another 3 minutes on top speed.
• Add the butter slowly at room temperature over several minutes then scrape down the sides of the bowl.
• whisk for a further 10 minutes on medium speed.