For simple meringues, beat four large egg whites in a mixing bowl and add 1/2 cup caster sugar until the mixture is thick and glossy. Fold in 1/2 cup icing sugar, place spoonfuls of the mixture onto a baking tray, and bake at 212 F for approximately 90 minutes.
Preheat a fan oven to 212 F, or a conventional gas oven to 230 F. Beat four egg whites in a large, non-plastic mixing bowl at medium speed using an electric hand whisk until the egg whites are fluffy and stand in peaks when the mixer is lifted. Increase the speed and add 1/2 cup of caster sugar, one spoonful at a time. Beat for about three seconds between each spoonful. Once the mixture is thick and glossy, fold in 1/2 cup of icing sugar by sifting one-third of the sugar at a time over the mixture then gently folding with a metal spoon or a spatula. The mixture should be smooth and billowy.
Place heaping spoonfuls of the mixture onto a baking sheet. For a fan oven, bake for 90 to 105 minutes, and for a gas oven bake for 105 minutes. The meringues are ready when they are a pale coffee color and sound crisp when tapped underneath. Leave them to cool and serve two meringues joined together with whipped cream.