First, amateur here (with aspirations for more, of course!)  I am making several kinds of truffles for a fundraising event at my church this weekend, and I made three different ganaches yesterday with the hopes of piping them into molds last night.  I missed my target and ran out of time.  I'm ready to pipe them tonight, but the ganaches have set and are quite stiff.  Is there any way to soften the ganache in the bag so that I can pipe, or must I start over?  (My hunch is that if I try to "micro" the mass, it will upset the fat content and lead to separation, correct?)

Any feedback is much appreciated!

I have used previously made ganaches quite often. I don't think it is wise to try to soften them in the bag as it would lead to very uneven melting and possibly separation. I slit the bag open and spoon out the ganache in fairly small pieces into a pot placed over hot water. Stirring constantly and mashing it a bit, I let it melt. I use an immersion blender if there is any separation. I am careful not to let it get over 80F. Then I spoon or pour it into a new pastry bag and pipe into shells. I have never had any problems with a ganache using dark or milk chocolate. White chocolate requires more care: a gentle heat and definitely an immersion blender to keep it from separating. Good luck.

Thanks, Jim.  Before I got your note, I tried reviving the ganache while still in the piping bag, so I now know what you mean to remove it from the bag first then proceed with the re-warming process.  Experience is a heckuva teacher, no?!