The main ingredient is of course icing sugar, which I mix with water and Meriwhite. If you require exact ingredients for the Meriwhite, please do not hesitate to contact me.
I am in the process of trialing a gluten-free mix in my royal icing. It produces good results in terms of taste and looks but I am still working on the consistency for posting them. If you would like to collect gluten free biscuits then these are available for a small supplement – please ask!