I'm gonna add my tuppence worth here.
The best fairy cakes/cup cakes/muffins are made from fairy cake batter, which are put into muffin cases.
Followed by adding the best icing, which is from the packets one finds in the supermarkets for royal icing like Tate and lyle .
The secret is to make sure that you only have a tiny bit of batter in the muffin cake a maximum 1 teaspoon, this then leaves room for the icing which you flood on top. Leave the cakes with the icing to set for half an hour before adding the decorations of your choice, sweets dolly mixture etc.
I have made these and sent them to school for my childrens birthday's and all the other kids go mad for them cos they really look and taste great.
Hope this helps