Ok so I know that buttercream gets great results under fondant, does anything else? I heard ganache but it is poured warm rigth? So then how does it cover the cake itself without showing lumps... cakes have lumps before it gets hidden under the BC. Can someone pleaSe tell me how to do it right to get that smooth finish and does it dry up enough so the fondant doesn't slide off? Or any othe mediums u Can think of. I just cant keep using just BC. Thanx in advance.

The ganache that you use under fondant is not poured fondant. It is a thicker ganache that is spread on the cake (I like to use it whipped - Yummy). If you look up how to cover a cake with ganache you will find plenty of info on how to make it/apply it.

Another question...will the ganache be seen through the white fondant?

Ganache is different to just a chocolate glace. You don't pour it over the cake. It has a consistency like nutella or soft peanut butter and you apply a more or less thick layer around the cake as you would using buttercream. Yes, you melt the chocolate to make ganache and it's warm, but you let it cool until it becomes spreadable.

Also if you look at my avatar picture the cake is done is white chocolate ganache made with a 3 part white chocolate/1 part whipping cream by weight so you can see that if you were to put fondant over the cake it would work beautifully. The ganache was firm enough for me to pick up with my hands on the ganache and put into a box the next day. I know this because my MIL got sick and I had to freeze the cake in a box that it only just fitted in. I was planning on serving it straight from the board it is sitting on so hadn't put it on a larger base board so had no other way to pick the cake up to put it in the box lol.

What the others said.... a batch of freshly made ganache needs to rest overnight (dark chocolate) or 24-30 hours (white chocolate) before it gets to the perfect consistency.  You can speed up the process by popping in the fridge or freezer.  If it 'sets' too far in the bowl, simply rewarm in the microwave in 10 second bursts and stir each time until you get back to peanut butter consistency.

Once on the cake (either exposed or under fondant) it sets really firm and handles hot days really well.

Roll your fondant to 3mm or more thick (sorry, dont know what 3mm is in inches) that way the dark chocolate colour will not show through under the white fondant.

If you accidentally get some ganache on your fondant, then wipe off with clear alcohol (ie rose spirit, vodka)