Preheat oven to 100 C. Place all ingredients in the bowl of an electric mixer and beat for 15 minutes until smooth, glossy and when you rub a little mixture between your thumb and index finger you cannot feel grains of sugar. Draw a 24 cm circle on a sheet of baking paper - easiest to draw round the edge of a cake pan.  Place the baking paper on an oven tray and pile the mixture into the circle, smoothing edges.  Bake for 1 1/2 hours and then turn off the oven and allow to sit in the oven with the door closed for at least another hour or until the oven is cold.