Preheat the oven to 200ºC/ 180ºC Fan/ Gas 6/ 400º F.
Line a baking tray with baking paper and add the caster sugar, put the tray in the oven for 7 minutes.
Meanwhile, measure the egg whites in a mixing bowl and whisk to soft peaks using a mixer or handheld electric whisk. Whisk slowly to begin with then increase the speed to medium until soft peaks form – about 5 minutes.By now your sugar will be hot so you can remove it from the oven and add it to the whisked egg whites a spoonful at a time. Keep whisking until the mixture is thick, glossy and bright white – about 7-9 minutes.
Turn your oven down to 100ºC/80ºC Fan/Gas 1/2/ 225ºF.
Check the mixture is done and all the sugar has dissolved by rubbing some of the mixture between your fingers. If you can feel any grain, continue to whisk for a couple more minutes until it feels completely smooth.
Use a dinner plate to trace a circle on your baking paper then take a teacup, mug or small bowl and trace another circle inside it. Flip the baking paper over (so the tracing doesn't transfer to the meringue) and secure it to the baking tray using a few dots of meringue mixture.
Dot tablespoonfuls of meringue mixture in a wreath shape onto the baking paper. Use the tracing as a guide. Pile the meringue up until you have no mixture left.
Make a well in the centre with the back of a spoon.
Put the baking tray in the oven and bake for 2 hours or until the meringue wreath can be easily lifted away from the baking paper.
Once baked, switch off the oven and leave the door open until the meringue is cool. Don’t be tempted to take it out and remove from the tray too early or it might break!
When the meringue is completely cool, lift it away from the baking paper and transfer it to your serving plate or cake stand.