Why did my fondant icing crack and dry out?

Rolled fondant is sugar held together by glucose, glycerine and a small amount of water, and it starts losing that water the moment it leaves the packet. Every cracking fault is a version of the same story: the surface dried, or the sheet was asked to stretch further than it could. The order in which you smooth a covered cake matters more than almost anything else, because pulling the fondant down at the sides is what tears the top edge.

What you'll need

• Fondant at room temperature
• White vegetable fat
• Icing sugar or cornflour for dusting
• Two cake smoothers (optional)

Step by step

1. Warm and knead it thoroughly first.Cold fondant straight from the packet is stiff and cracks as soon as it is rolled. Knead until it is warm, smooth and pliable — several minutes. A few seconds in the microwave on low softens a very stiff block, but watch it closely.
2. Add fat, not water, if it is dry.A small amount of white vegetable fat kneaded through restores pliability. Water dissolves the surface, makes it sticky and then dries to a harder crust than before.
3. Roll to 4–5mm, no thinner.Thin fondant tears at the corners, shows every lump underneath and dries almost immediately. Marzipan or a buttercream crumb coat underneath gives it a smooth surface to sit on.
4. Work fast and keep spares covered.Fondant starts drying in minutes. Anything you are not using goes in a bag or under cling film, and offcuts crust before you can re-use them if left out.
5. Lift it over the cake, do not drape and pull.Roll it loosely over the pin and unroll it across the cake. Then smooth the top first, then the upper sides, easing the skirt outwards with your palm so the fondant falls into place rather than being stretched down.
6. Smooth with two smoothers and light pressure.One in each hand, working round the cake. Hard pressure thins the fondant in patches and those patches crack. Trim the excess only when the sides are smooth.
7. Deal with cracks immediately.Rub the crack with a fingertip and a tiny smear of vegetable fat to close it. Larger tears can be patched with a thin piece of fondant blended in with fat, then covered by a ribbon or decoration at that point.
8. Store the finished cake at room temperature.Never in the fridge. Condensation on fondant coming out of a fridge makes it sticky, dull and prone to cracking as it re-dries.

Tips

• A buttercream or ganache crumb coat that has firmed up gives fondant a far better surface than jam or naked cake, and it hides irregularities that would otherwise show as thin spots.
• Cornflour dusts more lightly than icing sugar and dries the fondant less. Use it on dark colours where icing sugar leaves a bloom.
• Roll fondant on a large non-stick mat rather than the worktop. It moves without stretching and needs less dusting.
• Fondant offcuts keep for months double-bagged and airtight. Air is the only thing that ruins them.

Common mistakes

• Adding water to soften dry fondant — It dissolves the surface into a sticky film that dries harder and crackles. Vegetable fat is the correct softener.
• Pulling the fondant down the sides to remove creases — Every crease you pull out at the bottom becomes a stretched, thin, cracking patch at the top edge. Ease outwards, never down.

If it doesn't work