I was asked to make a bridal shower cake. They want fondant, can I pipe royal icing on fondant. I am teaching myself and I don't know if I can do this. Or do I pipe buttercream. If any one could help me I sure would appreciate it.
You can do either one--whichever makes you the most comfortable.
The royal will dry hard. If the cake undergoes any significant vibration, the royal could crack. A positive is that if you make an error, you can usually scrape it off and leave little, or no, evidence of the error.
The buttercream won't crack, but if you make an error and scrape it off, sometimes it will leave a grease mark.
I pipe on fondand with royal icing, for me the finish is a better match and has a smoother finish. I also find it easier to add flowers etc afterwards as it is set and can't be smudged.
If your cake is covered in a coloured fondant and you want a perfect match, you can also soften fondant in the microwave or by adding water a tiny bit at a time and pipe with it when it's cool.
I would use Royal icing too. Buttercream icing could fall off