4: Add more icing sugar a spoonful at a time, beating well each time. Continue until you have a smooth paste which leaves a point when you lift the whisk out.
5: Your royal icing is ready for use, to coat a cake or sweets, like calissons, for example.
Remarks
The proportions of egg white and sugar are fairly approximate. It is important to arrive at the right pasty texture, whatever weight of sugar you are using. The lemon juice gives a brighter whiteness, but you can colour royal icing with a few drops of food colouring if you prefer.