I'm making my sons birthday cake and want to know the BEST ganache recipe to use under MMF?! Can you even use ganache under MMF? If not, what do you suggest? Thanks so much!

I don't use MMF myself, but I can't see why not. I would use a 2:1 ratio ...so 1.2kg dark chocolate to 600ml cream (If using white chocolate then use 1.3kg chocolate per 450ml cream, as white chocolate is softer than dark.)