I would post a picture of what you see growing on top so someone with more experience than me can see what you're dealing with exactly. I would venture a guess that what you are seeing is mycellium growth which would be an awesome thing to see. As long as it's white and not some strange color or something, you probably aren't dealing with mold. From what I understand, that means you have some fungi in there and they are busy breaking down the additional amendments you added to the FFoF. If it were me, I would allow the mycellium growth to continue to do its thing for a bit, then gently turn it all over after a week or so. I would just monitor it and make sure you have a good moisture level going on in the bin it's "cooking" in and everything stays aerated and does't become anaerobic, other than that things should be just fine in there.
Again, a picture would probably help and someone with more experience and knowledge can chime in. These are just a few of the things I have picked up on in my limited experience with making my own soils. If nothing else, hope this helps put you at ease knowing your "mold" problem is most likely a great sign to the start of your soil.
