I've been working hard at getting nice straight clean edges with my cakes both buttercream and ganache (which I've really just started using), however I have a request for a 3 tiered marble cake, filled and frosted in ganache and covered in MMF, she doesnt want sharpe edges on the cakes she wants them to have the rounded edges, I have been doing the upside down technique to get the flat top and straight sharpe edges, so with this request would I just put the gananche on cake and put fondant over it when it sets, instead of doing the upside down technique. Any advice would be appreciated, I am new to ganache, and havent done the rounded edges with it.

I don't use ganache much, but I feel like it would be the same as frosting, look up the viva method. Take a flimsy piece of plastic (I use a cut out square from a yogurt/sour cream container) and use it to evenly round out the corners. On once the ganache sets a little, use your fingers to smooth out the corners.. Hope that helps!

Check this out on You Tube: Inspired by Michelle, she has 3 videos explaing ganache. Has helped me.

I try for square edges as well, but if I was trying to make rounded, I think I'd square my edges, then use a plastic edge to round them as described above, and possibly put a thicker layer of fondant, or even two layers on fondant on.