The science behind the perfect chocolate cake
By Benjamina Ebuehi Baking is such a simple way to invite a little bit of calm and joy into your life and, for some, nothing is more joyful than a slice of chocolate cake. There are many great recipes out there, and your perfect chocolate cake might be very different to mine. Whether you like it light and fluffy, rich and fudgy, or dark and damp, if you follow a few golden rules, it should come out perfectly every time. Baking is a science There are specific details in cake recipes, including my own, that may seem pedantic or fussy to the uninitiated – but believe me, they are there for good reason – and if you dig into the science behind them, it all starts to make sense…. Benjamina's chocolate cake is rich, fudgy and very easy to make. Begin with the butter I know some people choose to use margarine in their baking (Mary’s a devoted user of “baking spread” in her chocolate cake). And, margarine that’s made for baking can yield a lovely light, fluffy cake. But for me personally, it’s butter every time. Butter begins life as cream, whereas margarine starts out as vegetable oil, meaning margarine often has a higher water content and a lower fat content. Using butter ensures that crisp edge and a traditional round flavour. Choosing unsalted butter means you can control the salt level. (Although I always use salted butter for shortbread!) Some theories abound that salted butter may be less fresh, or of lower quality, but in my view it’s simply that they vary so much in salt quantity, you may find your cake a bit too salty. Don’t be tempted to race straight in with fridge-cold butter and milk. The fat in the butter entraps air when it is whipped, so when you cream your butter and sugar, you’re aerating the fat which creates lots of tiny air bubbles resulting in a light sponge. But if the butter is cold, the sugar crystals can’t penetrate the hard butter, meaning there’s no magic little bubbles of air. Room temperature ingredients also emulsify better, creating a seamless batter and ultimately a uniformly textured cake. Equally, if your eggs or milk are fridge-cold, or they’re added too quickly, the mixture's more likely to curdle as it can’t emulsify well with the other ingredients. A curdled mixture can make a heavier cake texture, so if this happens, just beat in a little of your measured flour. Which sugar makes the best cake? Brown and white sugar both have their own qualities, depending on the type of bake you’re going for – but for my perfect chocolate cake, I wanted to get the complex, caramel flavour of brown sugar for that fudgy finish. Creaming it can take a little bit longer because it naturally contains more moisture than white sugar. So, while it helps to keep the sponge lovely and moist, drier caster sugar aerates the butter faster. I’ve used light brown sugar, but dark brown sugar works if you like a deeply dark Devil’s food cake. A note on granulated sugar – it’s best not to substitute this into recipes that aren’t designed for it. It might hold up but the texture of the cake may be different. As I said, it’s all in the details. The Dutch process and raising agents Ok, here comes the science bit. I’m going deep on the two different types of cocoa powder. Dutch processed cocoa has been treated to reduce the acidity of the cocoa, giving it a milder and smoother taste. Natural cocoa powder is untreated and retains the sharp, almost citrus flavours that naturally occur in cocoa. Most UK brands tend to be Dutch processed, check for “acidity regulator (potassium carbonates)” on the label as that will be the giveaway. How is this relevant to your bake? Well, besides the difference in flavour, it affects which raising agent you use. Stay with me – let’s remind ourselves of the difference between bicarbonate of soda and baking powder. Bicarb is sodium bicarbonate, which requires an acid (e.g., lemon, buttermilk, or in this case chocolate) AND a liquid to activate its bubbles. Baking powder is bicarbonate of soda with added acid (usually cream of tartar), meaning it only needs a liquid to activate. Both work by giving off carbon dioxide which expands the little air bubbles we talked about earlier, helping the cake to rise. So natural, acidic cocoa powder is often used with bicarb, creating a light and airy bake, whereas Ph-neutral Dutch processed cocoa partners well with baking powder which already has the added acid. As a rule of thumb, bicarb is three or four times stronger than baking powder, so it acts as a turbo boost. So for this recipe, I’m using plain flour with baking powder and then a little bicarb for extra oomph, to work against that heavy melted chocolate. So I have more control I prefer to use plain flour and raising agents as opposed to self-raising flour. Sometimes the amount of raising agent in self-raising flour just isn’t enough to give the right lift. Formula for success Even though your perfect chocolate cake is very special, it is like any other cake in some ways. These cake tips will make all your cakes a bit better. Is sifting really necessary? Usually, no. For more delicate cakes, like the genoise in a Black Forest gateau, sifting is an important step to aerate the flour and makes it easier to fold in. If you are making a cake with cocoa powder, and bicarb, such as a red velvet cake you may want to sift it with the flour to distribute it evenly.Gently fold your ingredients with a plastic spatula or a large metal spoon whilst turning the bowl. If you just bung in your wet ingredients and flour, you’re more likely to get lumps in your batter (or start forming tough gluten trying to get rid of them). You may also lose all the air you whipped up by beating your butter and sugar together. Is sifting really necessary? Usually, no. For more delicate cakes, like the genoise in a Black Forest gateau, sifting is an important step to aerate the flour and makes it easier to fold in. If you are making a cake with cocoa powder, and bicarb, such as a red velvet cake you may want to sift it with the flour to distribute it evenly. Is sifting really necessary? Usually, no. For more delicate cakes, like the genoise in a Black Forest gateau, sifting is an important step to aerate the flour and makes it easier to fold in. If you are making a cake with cocoa powder, and bicarb, such as a red velvet cake you may want to sift it with the flour to distribute it evenly. Gently fold your ingredients with a plastic spatula or a large metal spoon whilst turning the bowl. If you just bung in your wet ingredients and flour, you’re more likely to get lumps in your batter (or start forming tough gluten trying to get rid of them). You may also lose all the air you whipped up by beating your butter and sugar together. Gently fold your ingredients with a plastic spatula or a large metal spoon whilst turning the bowl. If you just bung in your wet ingredients and flour, you’re more likely to get lumps in your batter (or start forming tough gluten trying to get rid of them). You may also lose all the air you whipped up by beating your butter and sugar together. Fold in flour with a light touch and a large spoon to retain those air bubbles Don’t hang around – once the batter is made, get it in the oven pronto because those raising agents are busy working away, and you need to capitalise on this chemical reaction so the heat from the oven can set those precious air bubbles.Make sure you use the tin size specified in the recipe – if you use a smaller one you risk the batter overflowing, and a tin that is too large will result in very thin, overcooked cakes!Make a little indent in the batter to compensate for that pesky hill shaped rise in the middle – if you do get a little hump, just cut if off and enjoy it as a baker’s bonus!Don’t be tempted to open up the oven to check on progress, you’ll let all the hot air out and your cake may sink.You’ll know your cake is ready when it’s sitting up proudly and it springs back when you press it gently – feel for the happy bounce. If you’re still not sure you can pop a skewer in – if it comes out clean, it’s ready. Don’t hang around – once the batter is made, get it in the oven pronto because those raising agents are busy working away, and you need to capitalise on this chemical reaction so the heat from the oven can set those precious air bubbles. Don’t hang around – once the batter is made, get it in the oven pronto because those raising agents are busy working away, and you need to capitalise on this chemical reaction so the heat from the oven can set those precious air bubbles. Make sure you use the tin size specified in the recipe – if you use a smaller one you risk the batter overflowing, and a tin that is too large will result in very thin, overcooked cakes! Make sure you use the tin size specified in the recipe – if you use a smaller one you risk the batter overflowing, and a tin that is too large will result in very thin, overcooked cakes! Make a little indent in the batter to compensate for that pesky hill shaped rise in the middle – if you do get a little hump, just cut if off and enjoy it as a baker’s bonus! Make a little indent in the batter to compensate for that pesky hill shaped rise in the middle – if you do get a little hump, just cut if off and enjoy it as a baker’s bonus! Don’t be tempted to open up the oven to check on progress, you’ll let all the hot air out and your cake may sink. Don’t be tempted to open up the oven to check on progress, you’ll let all the hot air out and your cake may sink. You’ll know your cake is ready when it’s sitting up proudly and it springs back when you press it gently – feel for the happy bounce. If you’re still not sure you can pop a skewer in – if it comes out clean, it’s ready. You’ll know your cake is ready when it’s sitting up proudly and it springs back when you press it gently – feel for the happy bounce. If you’re still not sure you can pop a skewer in – if it comes out clean, it’s ready. Further experiments I love a classic creamed butter-based sponge cake, but I also adore using olive oil in my baking (as does Nigella in her chocolate olive oil cake). It’s my favourite alternative to butter, bringing fruity tones and a beautifully moist crumb, plus it means you can create gorgeous vegan and dairy-free cakes. If you love a really moist chocolate cake, or can’t be bothered with a mixer, using oil is a good choice. A flourless chocolate cake, which you’ll now realise is the ultimate emulsion of melted chocolate, fat and eggs, sometimes with ground nuts to shore it up, is crisp on the outside, fudgy in the middle, and naturally gluten-free. Do embrace spice, citrus, nuts, fruits and floral tones in your cakes. People tend to shy away from vegetables in a cake but, like Mary’s beetroot chocolate cake, they can offer welcome earthy notes, especially when balanced with a sweet icing. And remember, when in doubt – choose cake. Originally published October 2022