Royal icing without eggs. This version is made with aqua faba but pipes and hardens just like the traditional version!
Place the aqua faba, cream of tartar and vanilla into a large bowl. Use an electric whisk or stand mixer to mix it up until frothy.
Add in half of the icing sugar and gently stir it in using a wooden spoon. Add the rest of the icing sugar and repeat.
Whisk it up again briefly, to make sure everything's well combined.
If adding colour to the icing, separate it into small bowls (1 for each colour). Use a toothpick to add the colouring a little bit at a time until you reach your desired colour.
Pipe or spoon the icing onto your cookies. Let each colour harden on the cookie before piping on the next if creating a layered design.