My three year-old came up with the idea of making grandma's birthday cake a stack of M&M cookies but out of cake. Any ideas on how to make this look good? Fondant or buttercream? I was thinking buttercream with kind of a marbled-brown tint and then pressing in the M&Ms. But I don't know how to make the texture look similar to a cookie. I'm moderately good at working with fondant so I can go that way. All ideas welcomed and appreciated.

I like your idea. Since I prefere working in b'cream I say go for it
Making the texture look like a cookie - maybe put small pieces of fondant under the b'cream? Like use cake spackle (cake crumbs mixed w/b'cream) and make it not smooth?

What a cute idea!!!! I see a future cake central~er on your hands...You could just use small cake layers and use like kakeladi said and mix the crumbs in with the frosting. It should be easy making them imperfect...But for me even imperfect never looks good enough...hehe. I try to perfect it all...Good luck I would LOVE to see pics when you are done!!!

Thanks for all the help. I went ahead with the buttercream and used crushed vanilla wafers for the textures. Here's the link.

http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1267810