There are many variations of this.  You can add or subtract the corn syrup depending on the consistency you want. The recipe can be halved, flavored and tinted. I made mine when the weather was hot and had to add tylose.
FROSTING, ICING ETC RECIPE HELP

INGREDIENTS
4 1/2 to 5 cups of Merkens Brand white candy melts
1 cup of light corn syrup. I use Caro and not a store brand. NOTE: If you want it less firm add less corn syrup. For softer fondant add more corn syrup.
3 1/2 to 4 lbs fondant, homemade or store bought; Don't use Merkens and Choco-Pan. They are too soft.

Powdered sugar, sifted; for kneading fondant

INSTRUCTIONS
1. Place the chocolate in a bowl and melt it in the microwave for short intervals making sure it does not burn. I start off with one minute and decrease the time once it starts to melt.
Stir the chocolate to make sure it has all melted. Add the corn syrup and stir vigorously to avoid oil coming to the surface. It will look like it has seized but that's fine.

2. Knead the white fondant on a surface sprinkled with powdered sugar.
FEARLESS BAKER, Premium Member, SAYS: “I use powdered sugar because I don't want the fondant-chocolate combination to get too soft. After the fondant is kneaded add the white chocolate that has the corn syrup in it and knead that into the fondant making sure it is well incorporated.”

3. Wrap very well in plastic wrap and set it aside in a resealable plastic bag. The fondant needs to firm up for about 3 days. The fondant will have to be kneaded again before you use it.  
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