Here's how to make the marshmallow fondant:
16 oz of mini marshmallows (usually comes up to almost a bag, give or take a few mini marshmallows)
2 pounds of icing sugar
Water
Shortening
Grease up a large pyrex bowl with shortening. Put in the marshmallow and add 2 to 5 tablespoons of water. Put in the microwave for about a minute. Stir and put back in the microwave until melted. Make sure you grease everything because it is incredibly sticky. When all the marshmallows are melted, you can either pour it into the icing sugar or you can add the icing sugar in one cup at a time. I prefer the second option. You will have to knead it as some point so it becomes like a dough. Grease your hands and the surface with the shortening. I haven't found a way for it not to stick to the surface or my fingers yet, despite the shortening. When it is kneaded, grease it with the shortening and wrap it well so it won't dry. You can use it after a little period of rest (15 minutes), but I usually leave it for the night. If there is too much icing sugar, it will be friable. If there is not enough, it will be sticky. It needs to be elastic enough so it can be rolled and put onto a cake. Color can be added either when it's made or after.
Here's one of our creation made out of marshmallow fondant, made for our nephew's birthday:
