This easy recipe is egg-free, chickpea-free, and uses pretty common ingredients. I think it tastes really nice as is, but also would lend itself to a variety of flavours. It pipes well (if only I had better piping skills!) and spreads well. I think leaving it out overnight to dry really sets it beautifully.
4 cups confectioner's sugar
2 tbs tapioca starch
1/2 tsp xantham gum
pinch of salt
4 tbs white corn syrup (I haven't tried but I think brown rice syrup would work but the colour will be a little off)
1 tsp vanilla (or a few drops of another extract for flavour)
approx 2 tbsp water
Using the bowl of a stand mixer, combine dry ingredients in a sieve or using a whisk
Add corn syrup, vanilla, and the first tbs of water. Mix on low. Add additional tbs of water at a drizzle until you have the consistency you want. For piping, less water will be better and for flooding, a looser icing works better.
Divide into bowls for whatever colours you are making, covering the ones you are not using with plastic or a damp cloth. Store in plastic bags or piping bags. Pro Tip: we use old infant medicine syringes to pipe--super easy for little hands and for the piping-challenged (moi). I also use a rubber band on the end of resealable plastic bags as piping bags (see note above).
Also, this version works very well for cookies, setting up glossy and smooth. It takes a while to set, so I found it less effective for gingerbread construction.