*Ensure there is NO trace of egg yolks in your whites and that your mixer bowl and whisk is completely grease free or your meringue won't stiffen.
** The buttercream may look like it's curdled at some point. Keep mixing until it is completely smooth.
*** You can make the ganache in advance and let it set overnight (with plastic wrap placed directly on the surface). It will be too thick at this point, so I microwave it for 5-10 secs and stir it until it's the right consistency.