Saturday, April 28, 2012

Don't Sweat the Aubergine - sponge cakes

A second extract from the new edition of my book Don't Sweat the Aubergine. The first edition gave no cake recipes, largely because I'm an inexperienced and inexpert baker. But it struck me that a book that purports to tell you how and why things work in the kitchen ought to have a section on this branch of cookery, in which, you could argue, some knowledge of the technicalities is particularly important.

I start with a bit of theory, and follow with three basic sponge recipes.

Sponge cakes

If a net is, according to Samuel Johnson, “holes tied together with string”, a cake may be described as bubbles contained by batter. You create the bubbles in three principal ways:

Beating (creaming) butter and sugar
Incorporating a raising agent, either by using self-raising flour or by adding baking powder (and/or, in some recipes, bicarbonate of soda, an ingredient of baking powder)
Creating an egg foam

The recipes here involve various permutations of these methods. But let’s start with the technical stuff, some of which applies not only to cakes but to other sweet things in this chapter.

HOW/WHY YOU DO IT
1) Equipment. Springform cake tins of 20cms and 23cms will cover a good many recipes. If you’re making a sponge sandwich, you’ll need two 20cm tins.

2) Lining and greasing the tin. Place the cake tin on a piece of greaseproof paper, draw round it, and cut along the pencil mark. Smear a very small piece of butter on the base of the tin, stick the round piece of paper on top, and smear a little oil on the surface of the paper and round the sides of the tin. Oil works better than butter as a non-stick agent, because the solids in butter can be adhesive.

3) Creaming. Generations of (mostly) schoolgirls suffered arm ache as they spent domestic science lessons – as they used to be known - mashing margarine, butter or some other shortening ingredient into sugar, and laboriously working away at the mixture until it lightened. These days, chefs tend to use hand-held mixers or food processors. Both machines require some manual intervention during the creaming process, because the mixture clogs up until it becomes properly amalgamated.

A creamed butter/sugar mixture, the texture of double cream, contains lots of air bubbles. It also separates the grains of flour, preventing lumps. This is why fats are known as “shortenings”: they interrupt the formation of gluten, which is a long chain of protein molecules.

4) Sifting flour. Unnecessary, despite what recipes may say. You are unlikely to find weevils left behind in your sieve; and any airiness you give to the flour now will be lost when you stir it into the batter.

5) Separating an egg. Crack the egg on the edge of a bowl, and allow the white to pour in. Gently, with your hand held over the bowl and your fingers straight, tip the yolk on to your fingers, opening them slightly to allow further white to slip through. Moving the yolk from hand to hand can encourage this process. (I got this technique from the opening sequence of a TV biopic of Elizabeth David.)

6) Whisking whites. Try to avoid letting any trace of yolk creep into the egg white. Don’t add salt or, despite what some experts recommend, lemon juice or vinegar: they soften egg whites.

I use a hand-held whisk, feeling that, in spite of the work involved, it enables me more accurately to judge the progress of the foam.

Use a large bowl, and tip it towards you, so that the whisk gets access to as much egg white as possible. You should stop beating when the whisk, lifted from the foam, creates peaks, which do not subside. It’s tempting to carry on, just to make sure you’ve got the right consistency. Resist. Further beating causes the peak stage rapidly to be succeeded by collapse.

7) Dropping the cake. In The Science of Cooking, Peter Barham offers the bizarre recommendation that, on removing the cake from the oven, you drop it from a height of about 30cms on to a hard surface. (An average ruler is about 30cms long.) The theory is this: as a cake cools, the air bubbles in it deflate, like collapsing balloons. Dropping the cake allows some of the bubbles to break, letting in air, which sustains the structure.

8) Turning out. Some recipes recommend that you wait five minutes, just long enough for the cake to contract from the side of the tin, before turning it out on to a wire rack. If you do this, place the cake top-side (the firmer one) down. I find that bits of cake stick to the rack anyway, and I usually allow the cake to cool in the tin.

Basic sponge
This sponge does contain a certain amount of gluten, which you create when you blend the flour with the sugar and butter, and when you stir in the eggs. If you have ever handled bread dough, which has a lot of gluten, you’ll know that it has an elastic quality. Here, that elasticity maintains the structure of the cake as the air bubbles expand. If the structure were to break and the bubbles to pop, the cake would collapse. The texture of the cake is, nevertheless, foamy.

100g self-raising flour (or plain flour, plus 1tsp baking powder)
100g caster sugar
100g softened butter
1tsp vanilla essence (optional)
2 eggs, beaten


Pre-heat your oven to gas mark 4/180C. Put in a baking sheet.

Line and grease a 20cm springform cake tin.2 – SEE HOW/WHY YOU DO IT, ABOVE

In a food processor, blend the flour, sugar, and butter, in short pulses, until you have a stodgy mass. Tip the mixture into a bowl, and stir in the vanilla (if using – I like it, but you may prefer less, or none at all) and a portion of the egg. Keep adding egg until you have a gloopy batter; it should drop off a spoon, but reluctantly. Don’t feel obliged to use all the egg; but, if you have done so before you get to the gloopy stage, add a little milk too.

Tip the batter into the cake tin, spread it out and level the surface, and put the tin into the oven on top of the baking sheet, which helps to convey the heat. Bake for about 25 minutes, or until an inserted skewer emerges clean.

Drop the cake tin from a height of about 30cms on to a hard surface (I hope the spring is secure).7 Allow the cake to cool before turning it out.8 I keep it in greaseproof paper, wrapped inside foil.

VARIATIONS
Add the zest of a lemon, or of an orange, to the mix. And/or poppy seeds. Or any other dry flavourings.

Make a sandwich: double the ingredients, and divide the batter between two tins, baking the layers side by side.

Fillings. You might go for a cream tea theme, with a layer of jam topped by whipped cream. Or try lemon curd, from Geraldine Holt’s Cakes: 1 lemon; 60g caster sugar; 1/4tsp cornflour; 1 egg; 30g butter. Use a small bowl that will rest in a saucepan of simmering water without the base touching the water’s surface. Grate in the lemon zest, and add the juice too, along with the sugar, cornflour, and egg. Cook the mixture, stirring all the time, above the simmering water. After about five to seven minutes, the mixture should start to thicken. Remove the bowl, and stand it in cold water; while the mixture still has some warmth, stir in the butter in small pieces. Allow the curd to cool before spreading it on the cake.

Victoria sponge
The same ingredients as above, but, you’ll notice, in a different order. Creaming the butter and sugar before adding the egg and gently folding in the flour results in a cake that is lighter in gluten, and that therefore has a lighter texture. The drawback is that the air bubbles are more likely to burst in the less elastic batter, particularly if your mixture is too loose.

100g caster sugar
100g softened butter
1tsp vanilla essence (optional)
2 eggs, beaten
100g self-raising flour (or plain flour, plus 1tsp baking powder)


Pre-heat your oven to gas mark 4/180C. Put in a baking sheet.

Line and grease a 20cm springform cake tin.2 – SEE HOW/WHY YOU DO IT, P000

Cream the sugar and butter until the mixture is soft and fluffy.3 Beat in about three quarters of the egg – this may be enough. Add the vanilla, if you’re using it, and gently fold in the flour. You should have a gloopy batter, which will drop off a spoon, but reluctantly. If the batter is too stiff, gently add more egg. If it’s still too stiff, add a little milk.

Tip the batter into the cake tin, spread it out and level the surface, and put the tin into the oven on top of the baking sheet, which helps to convey the heat. Bake for about 25 minutes, or until an inserted skewer emerges clean.

Drop the cake tin from a height of about 30cms on to a hard surface.7 Allow the cake to cool before turning it out.8 I keep it in greaseproof paper, wrapped inside foil.

VARIATIONS
See the suggestions below the basic sponge recipe, p000. Here’s an extra one: lemon drizzle. Put the zest and juice of two lemons in a bowl, and stir in 100g granulated sugar until dissolved. When you remove the cake from the oven, spoon this syrup all over it.

Genoese sponge
In this sponge, the eggs produce the foam – there is no other raising agent. A cake the size of the sponges described above would again have 100g of flour and 100g of sugar, but with four eggs, and 50g melted butter. You need an electric whisk to beat together the sugar and eggs; eventually, after a good 10 minutes and maybe more, they increase in volume by as much as six times, and become stiff and very pale. Then you fold in the flour. Last (because the fat collapses the air bubbles), you stir in the butter, quickly transfer the batter to the tin, and bake it as in the recipes above.

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