In short: Fondant is a pliable edible paste for covering and decorating cakes. At home it is made three ways — milk, marshmallow and gelatin based. The one rule that matters: fondant cannot tolerate moisture, so it needs a stable frosting underneath, such as buttercream.
What fondant is
Fondant is edible modelling paste. You can buy it in a cake shop or make it yourself. Several kinds exist, similar in their key properties but differing in composition and method.
Because it will not tolerate moisture, the frosting underneath matters more than the fondant itself: buttercream or chocolate ganache work, whipped and sour cream do not. To join pieces of fondant, water or egg white is ideal. Work in gloves so you do not leave fingerprints on the finished decoration.
Types of fondant
By purpose. Universal fondant is used both for modelling and for covering cakes. Modelling fondant holds fine detail but dries faster. Covering fondant rolls thin without tearing.
By composition. Milk fondant is made on condensed milk and milk powder, marshmallow fondant on melted marshmallows and icing sugar, gelatin fondant on bloomed gelatin — the firmest of the three and the best for figures.
Which to make at home
Marshmallow fondant is the usual starting point: two ingredients, no cooking and a forgiving texture. Milk fondant tastes better but is softer and harder to roll thin. Gelatin fondant is the choice when the decoration has to hold its shape.
Frequently asked questions
What frosting can go under fondant
Buttercream, chocolate ganache or cream cheese frosting made on butter. Whipped and sour cream fillings release moisture and the fondant will slump.
Why is my fondant melting on the cake
It has absorbed moisture from the frosting or the air. A fondant-covered cake should not sit in the fridge unless it is sealed.
How do I store leftover fondant
Wrapped in film against the surface and in a closed container at room temperature. Left in the open it forms a crust within half an hour.