I have used Marshmallow Fondant for a few cookies. I found that I really enjoyed playing with it AND it taste good!! An added bonus? It's super easy to make.
As far as applying to the cookie, you can do it a few different ways. I have actually used the corn syrup method. You just brush a very thin layer onto your cookie and apply the fondant. But my favorite way? Soon as your cookie comes out of the oven, place your fondant on the warm cookie. Instant glue It is so fast and easy.
Here is a blog post and tutorial I did on making marshmallow fondant:
http://tamirenascookies.blogsp...hmallow-fondant.html
Here is another blog with a couple videos on stamping fondant and how I apply them. Super easy and fun
http://tamirenascookies.blogsp...make-impression.html
Good luck!! Love to see what you come up with