Royal icing: frosting that hardens on drying

Useful to know

Royal icing is used for coating, decorating and assembling decorative biscuits. King Arthur’s recipe explains that it hardens as it dries and that unused icing should be covered. [1]

Separate only the colours needed for the current work and keep the remainder covered. Use the egg product specified by the recipe, which also provides a pasteurized egg-white option. Soft buttercream and a drying icing are not interchangeable. Establish whether the decoration needs to hold an outline, fill an area or remain soft.