method and the basic ingredients for a sponge should give you a good intro to the ‘ins and outs’ of baking cakes. You may want to skip this part and go straight to the recipe: you will still get a good result. I have always been fascinated by the science behind every step and measure and have found that understanding it (or trying to) makes the whole process more involving and leads to much better results. There are more rules for a baker than for a chef, and whether you follow them or not, it can be really useful to try to understand them.
BALANCING THE CORE INGREDIENTS Flour and eggs are the backbone of a cake; they give it structure, but can also dry it out. Sugar and fats make it soft and moist but can destroy its structure. A good sponge cake needs a careful balance of the core ingredients. A NOTE ON FAT IN CAKES Oil greases the proteins found in flour much better than butter does and makes for a more moist, tender cake; however, there is a difference in flavour. Experiment with replacing some of the butter in cake recipes with oil.
STEP 1: CREAMING THE FAT AND SUGAR ‘Creaming’ involves beating together the fat (butter) and the sugar and ensures that your cake will have a fine, even texture. Beating drives the sugar crystals into the butter, and their rough edges catch lots of tiny regular pockets of air that are trapped in a coating layer of fat. These pockets form the basis of the cake. (Caster sugar is best here, as its smaller crystals result in a higher number of smaller air pockets.) Eventually each of those little pockets of air will fill up with expanding gas and steam in the oven, making it rise with a texture that’s soft and light. How long this stage takes will vary according to your mixer – I recommend approximately 5 minutes, but you’ll know it’s ready when it looks lighter and increased in volume; this is what a recipe refers to as ‘light and fluffy’. TIP: Starting the mixer on low and then gradually increasing the speed allows the air bubbles to form and strengthen. Starting at too high a speed could break the fragile air bubbles, which will cause the finished cake to be heavy and dense. STEP 2: BEATING IN THE EGGS The next step is to beat in the eggs, which will seal the buttery air pockets and help prevent them from collapsing when the butter melts in the oven. Egg whites also contain proteins that set to hold the structure of the cake, and the yolks add tenderness and a creamy texture. Only beat to incorporate eggs; there’s no benefit to the cake in extra beating once they have been added. Over-beating at this stage can lead to a separated cake with a shiny ‘crust’. STEP 3: ADDING FLOUR, BAKING POWDER AND LIQUID Flour contains the makings of the gluten which, along with egg white, will form the foundation of the cake’s structure | see notes on on page 19 |. Once flour has been added, beating should be kept to a minimum, to restrict the development of too much gluten (enough will support your cake, too much will give it a heavy, fibrous texture – more like bread). BAKING POWDER: Should be whisked evenly into the flour before it’s added to the batter | see note on chemical leaveners, below | – I find sifting them together is not enough to combine them evenly. LIQUID: The right balance of liquid will give the cake structural support by helping to form gluten, add tenderness and convert to steam once in the oven, allowing more air to be released into the batter. I usually carry out this stage in three parts, adding half the flour, then the liquid, then the remaining flour – this keeps the batter from splitting but prevents too much gluten forming. Just remember not to over-beat. STEP 4: BAKING Once exposed to the heat of the oven, the volume of your cake will increase and its structure will set. This is due to multiple events that take place in the batter. First, the heat causes the gases in the air pockets to expand, which in turn stretches out the gluten structure. At the same time the acid and alkali in the baking powder will react, releasing carbon dioxide, which will expand these pockets even further. Then, as the temperature creeps up, the liquids begin to steam and expand the air pockets once again. Eventually the egg in the batter will set (coagulate) and the gluten will lose its elasticity, sealing the structure of the cake. The sugar will then caramelise and give it a lovely brown finish. The temperature of your oven is key here – if your temperature is right, the timing of the expanding air pockets and melting of the fat should coincide with egg film coagulating and seal the air pockets in the cake’s structure. If the temperature is out, these events might not sync so smoothly and your cake will be spoiled.
BICARBONATE OF SODA OR BAKING POWDER? Bicarbonate of soda and baking powder are two kinds of chemical leavener or raising agent. When bicarbonate of soda (sodium bicarbonate) is combined with moisture and an acidic ingredient (e.g. cider vinegar, yoghurt, soured cream, chocolate, buttermilk, honey) the resulting chemical reaction releases carbon dioxide bubbles that expand in the oven and help your bakes to rise. This will start to happen as soon as you mix the bicarbonate of soda and the acid together in a batter, so try to get it into the oven quickly. Baking powder is a blend of acid (cream of tartar) and alkali (sodium bicarbonate). Although the acid and the alkali are already combined, they will only start to fully react when exposed to the heat of the oven. Which of the two leaveners you should use will depend on your other ingredients: bicarbonate of soda needs an acid to balance it (and to react with) so it’s best used in a recipe containing an acidic ingredient – if you ever accidentally substitute bicarbonate of soda for baking powder in a recipe with no acid ingredient to balance it, you will notice a very bitter, soapy taste. Baking powder has a more neutral flavour. Don’t try to substitute one for the other without adapting the rest of the recipe. In most cases, if a recipe asks you to use both, the baking powder is likely to be acting as the main leavener, while the bicarbonate of soda will be there to neutralise an excess of acid from the other ingredients. NOTE: Measure chemical leaveners carefully; a little goes a long way. As a general rule you should use 1 teaspoon of baking powder or ¼ teaspoon of bicarbonate of soda per 130g of plain wheat flour.
IF YOUR OVEN IS TOO HOT the edges of the cake will crust before the middle has a chance to fully bake, leaving a soggy centre full of gases that continue to expand late in the baking process and cause your crust to crack. IF YOUR OVEN IS TOO COLD the fat will melt, releasing its air and leavening gases before the other elements in the batter set to hold them in place, and the cake won’t rise. COOLING You should generally leave a cake to cool in the tin for at least 10 minutes after removing it from the oven, placed on a wire rack so that air can circulate. Cakes are softer and more fragile before they are fully cooled – the cooling process allows the flour’s gelatinised starch to gel and firm up the cake, and if you try to remove it too soon, it will likely stick to the tin. If you leave the cake in the tin too long, the steam it releases will be trapped and make it soggy. After 10 minutes, remove it from the tin and leave it on the wire rack to cool. It’s best to wait until the cake is completely cool before peeling away any baking paper, otherwise you might take chunks of cake off with it. STORING Cakes generally keep well at room temperature for a few days, thanks to the moisture-retaining properties of the butter and sugar they are made with. Icing a cake will help to preserve it for longer, as less of the cake is exposed to the air. Putting cakes into the fridge tends to dry them out, but you can freeze most cakes. Just wrap the un-iced cakes tightly in a thick layer of clingfilm and defrost at room temperature.
CAKES MADE WITH WHIPPED EGGS
OCCASIONALLY a recipe will call for whipped egg whites, and in this case the cake batter is getting some or all of its leavening from air trapped in the beaten whites. This process requires beating the whites to a rich white foam, filled with air bubbles. These expand in the oven until the egg sets and seals the air in place. When it comes to whipping egg whites for a cake the rules are strict, but don’t be put off – it’s actually very simple and you’ll probably nail it first time. As with making meringues, you need to use room temperature eggs and separate them carefully, as fat from the yolks will spoil the process | see page 20 for how to separate eggs |. In fact any fat or grease is your enemy here, so make sure everything is really clean.
WHIPPING EGG WHITES Ideally use a stand mixer with the whisk attachment or hand-held electric whisk
