I use a bag of Marsh mellows, about teaspoon of water and powdered sugar. Melt marshmallows, with water, in microwave, then I knead in the powdered sugar until it feels like play dough. There is an exact recipe, for marsh mellow fondant, but I don't remember it. I like to just go by feel. If I am coloring it I add it before the powdered sugar for easier mixing.