2 baking-sheets which must be spotless or covered with silicone baking-paper
Preheat the oven to 110°C/225°F/Mark ¼. Melt a dessertspoon of butter and use it to brush the two baking-sheets. Sift a light shower of flour over the entire surface, shaking the tins lightly to remove excess flour. Using a round biscuit-cutter, or a cutter in any shape that you would like the meringues to be, mark out the baking-sheets by pressing it into the flour. This will help you to be accurate when you are piping out the meringue.
Clean the interior of a large mixing bowl with half a lemon. The lemon juice will remove any trace of grease from the surface, which might otherwise prevent the egg whites from rising properly. Rinse the bowl in cold water and dry it well. Put the egg-whites, without a trace of yolk in them, into the bowl. Whisk steadily, beating with an upward movement to incorporate as much air as possible with the egg whites. After 4 or 5 minutes, when they have started to rise, add half the sugar and continue whisking. When they have become very firm pour in the remaining sugar in a light shower, continuing to whisk.
When the whites have risen well and are firm transfer them immediately to the pastry bag. Pipe out the meringues on to the baking-sheets in the shape you have decided on. Put them into the low oven for 2½ hours. To help prevent them from becoming brown insert a third baking-sheet on the shelf above the meringues. When you take the meringues out of the oven allow them to cool and then put them in an airtight container, which should be kept in a warm, dry place. They will keep like this for several days.