Sift your flour 3 times onto a sheet of greaseproof paper, this helps develop the air in the cake. Pop your eggs and sugar into a large bowl and place this over a saucepan of boiling water creating what's better known as bain-marie. Be sure that the bowl isn't touching the boiling water. Beat this with your electric whisk until the mixture is thick and fluffy. If you lift the whisk out and create a figure of eight you'll be able to see it, that's when it's ready.