I just found this in an old depression ad
Yellow Icing for Jack o’Lantern Smiles:
1 egg yolk 1-1/2 cups confectioners’ sugar
1 tsp melted butter 1 tbsp orange juice
1 tbsp grated orange rind
Break up egg yolk with fork. Add sugar alternately with the butter and orange juice. Add the orange rind.
I'd only do this if you have farm fresh eggs that you can trust and orange rind that you are sure hasn't been sprayed. Looks fun!