Sweet Art Factory.com under recipes, has what she calls "Faux Fondant" made from marshmallows. Here is a copy and paste of her recipe for you.
Faux Fondant Recipe
Go to our "How to Guides" to get step-by-step instructions on how to create this easy to make Faux Fondant. You can purchase the gum paste mix (2 oz. jar) in our online store. You can substitute almond flavoring for any clear extract/flavoring of your choice.
You Need:
1 16 oz. bag of Minature Marshmallows.
2 LB. Confectioners Powdered Sugar (sifted if possible)
2 Tbsp. Gum Paste Mix (we sell a 2 oz. jar)
1 Tbsp. Clear Almond Extract
How to Make:
In a microwave safe bowl, add marshmallows. Heat for 30 seconds at a time until melted, stirring each time. DO NOT OVERHEAT. Add extract and stir well.
In a large bowl, mix powdered sugar and gum paste well. Make a well with the sugar (see how-to-guide). Pour melted marshmallows into center. Slowly bring powdered sugar into the marshmallow mix, not allowing marshmallow mix to touch the bow.
Keeping kneading the mix until you get a nice dough. If not using immediately, store in an air-tight container until use. It will keep for many weeks.
Add color gels to create many variety of fondant colors.
Once fondant is made, you are ready to roll it out to create decorations for cakes and cookies. Use cornstarch instead of flour to dust the work surface and rolling pin.