I'm all about marshmallow fondant, usually can make it without issues, but occasionally, like tonight, I encountered a problem with it. I made 3 batches. Two of the three had perfect consistency. The third and last when I kneaded the sugar into it I could tell wouldn't work out. It seems to shred or rip apart while kneading. I tired adding more Cisco, nope. Nuking it for a few seconds, nope. It's like It lost all elasticity.
Thoughts? I don't want it to happen again!
What about adding a drop or two of glycerine, that should help with elasticity. Also it might benefit from a bit of rest, just to let all the moisture absorb and distribute.
some people add little glycerine , some add glucose or white syrup. this is a good site to read. hth