Most cakes are not ruined in the oven. They are ruined in the twelve hours between finishing and serving, usually by being stored in the wrong place or carried on somebody’s lap.

Sponges you have not decorated yet

Let them cool completely first. A warm sponge wrapped in cling film steams itself and goes sticky. Once cold, wrap each layer tightly and keep it at cool room temperature for a day or two, or freeze it, still wrapped, if you have baked ahead. Frozen sponge is easier to level and to fill than fresh, so baking a day early is a real advantage rather than a compromise.

A finished buttercream cake

An airtight box at cool room temperature is usually better than the fridge. A fridge dries a cake out and it will pick up the smell of whatever else is in there. If the room is warm, which in a Cape Town summer it usually is, chill the cake instead, then take it out an hour or so before serving so the buttercream and the sponge come back to a soft, edible temperature. A cake served straight from the fridge tastes dense and dry, and that is the temperature, not your recipe.

Fondant does not belong in the fridge

Fondant and condensation do not get along. A fondant-covered cake taken out of a cold fridge into a warm room sweats, goes sticky, and the colours can bleed into each other. Keep it covered in a cool, dry place instead, out of direct sun.

When the fridge is the right answer

Anything with fresh cream, cream cheese frosting, custard or fresh fruit on it belongs in the fridge, and goes back into the fridge as soon as it has been served. Follow the guidance for whatever you filled it with rather than for the cake as a whole. If you are not sure, refrigerate it.

Boxing it

Put the cake on a board stiff enough not to bend when you lift it, and use a box the same size as the board rather than a bigger one. A cake with room to slide will slide. If the box is a little large, a non-slip mat or a folded cloth in the bottom stops the board moving.

Close the box before the cake goes into the car, not once it is already in there.

Getting it there

• Flat floor, never a seat and never a lap. A seat is sloped and a lap moves.
• Air conditioning on and pointed away from the box, especially in summer.
• Brake and turn earlier than you normally would. Most damage happens at one sharp stop.
• Take a small tub of the same buttercream, an offset spatula and a few spare decorations. A five minute repair on arrival is normal, even for us.

Boards, boxes, non-slip mats and the rest of it are in the shop: shop baking supplies.

You open the oven, the cake looks perfect, and twenty minutes later there is a crater in the middle of it. It is the most common thing that goes wrong in a home kitchen, and it is almost always one of these six.

1. The oven door was opened too early

A cake rises because steam and gas push the batter up before the structure sets. Open the door before that structure has set and the cold air drops the middle straight back down. Leave it alone until at least three quarters of the baking time has gone. If you need to turn the tin, do it quickly, and late.

2. It was not actually baked

A browned top is not the same as a baked cake. Test in the centre, not near the edge: a skewer should come out with a few dry crumbs and no wet batter on it. The cake should also have started to pull very slightly away from the side of the tin, and the top should spring back when you press it lightly.

3. Too much raising agent

More baking powder does not make a better rise. It makes a fast rise with nothing to hold it up, so the cake climbs and then falls. Measure it level rather than heaped, and check the date on the tin. Old baking powder is a different problem with the same ending.

4. The batter was overmixed after the flour went in

Creaming butter and sugar properly is worth the time. Beating hard once the flour is in is not: it builds the gluten that makes a cake tough and it knocks out the structure you have just built. Fold the flour through until it disappears, then stop.

5. The oven is not the temperature it says it is

Most home ovens run hot or cold, some of them by a lot, and nothing on the dial tells you which. An oven thermometer is inexpensive and it answers the question in one bake. Too hot sets the outside before the middle has finished rising and the middle then falls; too cool and the cake never sets properly at all.

6. The tin was too small, or too full

Fill a tin about two thirds. Any fuller and the batter rises higher than its own structure can support. If you have batter left over, bake it as cupcakes rather than forcing it into the tin.

What to do with the one that sank

Do not throw it away. A sunken cake is still a good cake with a dip in it. Level the top off with a serrated knife and use it as a bottom layer, where the filling and the sponge above hide everything. Or break it up into a trifle, or roll it with a little buttercream into cake pops. Nobody eating it will ever know.

Baking theory, why sponges behave the way they do, and the mistakes worth avoiding are the whole first half of the baking class: see the classes.