Marshmallow fondant is easiest to prepare but can lack the crisp finish of classic fondant. Classic rolled fondant can be made at home, but is slightly more complicated and fickle in preparation.
To prepare marshmallow fondant, combine 16 ounces of high-quality, white mini marshmallows and 2 tablespoons of water in a large, microwave-safe bowl. Microwave, stirring every 30 seconds, until completely melted. Pour 3/4 of a 2-pound bag of confectioner's sugar over the marshmallow. Heavily grease hands and countertop or plastic cutting board with vegetable shortening. Dump the marshmallow mixture into the middle of the greased space, and knead the dough, incorporating the remaining sugar and regreasing hands and counter as needed. At the start of kneading, the dough is incredibly sticky.
For rolled fondant, sift 2 pounds of confectioner's sugar into a plastic or glass bowl. Place 1/4 cup of cold water in a small saucepan and sprinkle 1 tablespoon unflavored gelatin over the top. Allow gelatin to soften for five minutes before beginning to heat. Stir gelatin constantly until dissolved. Do not boil. Turn off the heat, and add 1/2 cup white corn syrup and 1 1/2 tablespoon glycerine, stirring until well-blended. Pour the gelatin into the sugar, and mix until well-blended. Knead the dough until soft, adding more sugar if the dough is too sticky.
Both doughs can be colored by adding food coloring while kneading. If the dough tears, add water until dough is stretchy. Double-wrap prepared dough of choice in plastic wrap, and allow to rest for several hours at room temperature for best results.