Here are some tips on how to make the perfect meringue:
One of the golden rules of meringue making is that all of your equipment must be scrupulously clean, without a speck of grease, or it will be much more difficult to produce the desired foam with your ingredients. Rub your mixer bowl with half a lemon before beginning, to eliminate any last specks of fat before you beat the egg whites.
There are other tricks the cunning chef can employ to improve the chances of achieving a stable foam. The most common is adding a little acid, such as vinegar, more lemon juice, or cream of tartar, to the mixture, after the sugar.
Caster sugar is the usual option for meringues – the small grains dissolve easily in the foamy mixture. However, you can take this a step further, by using half caster and half icing sugar.
Most recipes call for the sugar only after the whites have been whipped to soft peaks – add it too early and you can kiss goodbye to a good strong foam.
100C is too high. Put them in at 60C, 70C, overnight. You don’t cook meringues so much as dry them out, apparently; evaporating the water to leave only the rigid structure of the egg and sugar mix, and the air bubbles in between. Depending on the size it can take about 6 hours to make your perfect meringue.
Meringues need clean equipment, good sugar, and, most important of all, a low oven.