This is the fondant icing recipe we almost always turn to when we make fondant-covered birthday cakes. The reason we say we almost always use it is because it's time-consuming. It's worth the effort, though. And if all you know of fondant is that store-bought stuff...well, this is gonna knock your socks off.
(If you'd rather use a quicker and super easy rolled fondant recipe, try this one for marshmallow fondant.)
We adapted this classic fondant icing recipe from Rose Levy Beranbaum, the author of The Cake Bible. If you've never checked out that cookbook, you really must! It's worth it for the photographs alone.
Note: if adding flavoring, reduce water by the same amount.
Sprinkle the gelatin over the water (and flavoring, if desired) in a microwave-safe bowl and let it sit for 5 minutes. Heat for 15-20 seconds or so in the microwave until the gelatin is dissolved.
Stir in the corn syrup and glycerine, then add the vegetable shortening and stir until melted.
Place the powdered sugar in a large bowl and make a well in the center. Add the gelatin mixture and stir with a wooden spoon that's been lightly greased with shortening. Stir until blended.
Grease your hands lightly with shortening and knead the mixture in the bowl until most of the sugar is incorporated.
Turn the dough out onto a large, flat and lightly greased surface (a very clean kitchen counter or table top work well) and continue to knead until the dough is smooth and satiny. If the fondant seems too dry you can add a few drops of water and knead again. If it's too sticky, add a bit more powdered sugar and knead until it's incorporated.
The fondant should be soft, smooth and pliable but not sticky.
Wrap the fondant tightly in plastic wrap and then place it in an airtight ziploc bag. Let the fondant rest for several hours. This makes it easier to work with. The fondant will firm up a bit after resting. You may want to warm it in the microwave for a few seconds before working with it, especially if you've let it sit overnight. When you're ready to roll it out, spray your work surface and your rolling pin with a light coating of nonstick vegetable spray.
The fondant will keep for 1 month at room temperature and can be frozen indefinitely.