This is my go-to recipe for decorating gingerbread men, Christmas cookies and cakes; it works wonderfully and has a beautiful smooth finish. For a thicker consistency, add more icing sugar. Add food colouring or flavour extracts if desired.
You can mix the icing by hand using a wooden spoon if preferred. Add the icing sugar gradually, mixing well after each addition until it is well incorporated with the egg whites.
Use or store in the fridge for up to 2 days if covered with clingfilm.