I noticed on the show Cake Boss that Buddy puts a regular layer of buttercream under his layer of fondant. How do you do that and not get the bulging out or ruffling? I have seen ganache under fondant but I want to do a regular layer of buttercream. I want to learn how to do it and get no bulge and sliding. I want straight up and down sides. And be able to use a thin layer of fondant.

Fill and crumbcoat the cake, let it settle for about 12 hours (overnight). Then ice the cake and chill just until the buttercream is stiff. Make sure the buttercream is smooth, any ridges are gonna show through the fondant. Then roll out your fondant and cover.

Thank you.

http://jessicakesblog.blogspot.ca/2011/06/video-tutorial-upside-down-frosting.html

HTH