I am using a recipe that I found here for Buttercream Flavored MMF. I have never used fondant before so I am unsure of exactly how the consistency should be, etc. However, I know there needs to be some elasticity in order for it to lay on the cake correctly.

The batch that I made this morning is constantly tearing when I try to use it. I have kneaded it repeatedly and added Crisco, but it does not seem to be helping. Have I not let it rest long enough or is there something else that could be the issue?

I always let my homemade fondant rest 24 hours before trying to use it. If you made it this morning, I think your MMF is too fresh. Try using it tomorrow and see if it gets any easier.

If that doesn't work, try making another batch. I sometimes have a "bad" batch of MMF here and there, and I have read on here that others run into that too, sometimes.