Does cocoa powder mix well with this recipe and if it does how much cocoa powder would you add to make a chocolate MMF.

If you do a search for Chocolate MMF you will get lots of answers!

In the meantime:

For Chocolate Marshmallow Fondant:
Add 1 oz melted chocolate.
1 tbsp cocoa powder to the basis recipe.
Chocolate fondant..........I add good quality chocolate to my marshmallow fondant. I prefer Lindt or Ghirardelli. It just makes it taste better. I want everything to be palate pleasing. You can add candy melts if you so choose. There is nothing wrong with that at all. Just depends on your taste buds.