I did a cake a few weeks ago covered in MMF and the customer told me today (while ordering another cake) that the MMF was a bit waxy. I made the cake on a Wednesday night and he picked it up the following evening. It sat on my counter until he picked it up.

What would have made it waxy?? Do you think she just doesn't know the nature of fondant? Now I'm concerned. Thanks in advance for your help.

I can't think of a reason why MMF would be waxy!? Did you add a food coloring or flavoring? I have made MMF several times and never have had this problem.

Depending on the recipe it only has marshmallows, water, flavoring and p. sugar...I have made it MANY times and never had any waxy texture/flavor. Sounds like maybe they just do not like the texture of fondant? Some people like the look of it but not the flavor- even MMF! Crazy, I love it!

I'm not sure either. I added americolor gel in turquoise, copper, and deep pink. I'm thinking that she just doesn't know the nature of fondant in which case I'm concerned because the cake she ordered today is also covered in fondant.

I cannot think of a reason why it would be waxy..
unless she just used a term that didn't really fit the description on how it really was. Has she ordered fondant from you before ?
It is texture or taste ? next time she comes in, let her taste the same kind of fondant and ask her if it tasted like that ?