Earlier today the Croxii collectively attended my sister’s birthday party, which was held at her family’s beach hut on Cromer West Beach (the déclassé end of Cromer, if you ask me, but we’ll let that pass)
Cromer West Beach, earlier today.
… and Mrs Crox baked a chocolate cloud cake for the occasion.
The cake was gluten-free, and you can find the recipe on page 110 of Nigella Bites, by
voluptuous sexpot celebrity chef Nigella Lawson. The recipe goes like this:
for the cake
250 dark chocolate, minimum 70% cocoa solids;
125g softened unsalted butter;
6 eggs (2 whole, 4 separated) – laid specially by our hens;
175g caster sugar;
2 tablespoons Cointreau (optional);
Grated zest of one orange (optional);
for the topping
500 ml double cream;
1 tsp vanilla extract;
1 tbsp Cointreau (optional);
1/2 tsp unsweetened cocoa powder.
Melt the chocolate, and let the butter melt in the warm chocolate.
Beat together the two whole eggs and four egg yolks with 75g of the caster sugar, gently add the melted chocolate, Cointreau and zest.
In another bowl, whisk the four egg whites until foamy, then gradually add the 100g of sugar and whisk until whites are holding their shape but not too stiff. Lighten the chocolate mixture with a dollop of egg whites, then fold in the rest of the whites. (Yes, Nigella uses the word ‘dollop‘.)
Pour the lot into a cake tin lined with baking parchment and bake for 35-40 mins at 180 degrees Centigrade (Gas Mark 4). Leave to cool.
For the topping, whip the cream until it’s firm but not too stiff (I did this, by hand – it took half an hour, with necessary motivational force provided by listening to a selection of live recordings of my beat combo Stealer), splosh in the vanilla essence and Cointreau during the process, then spread on top of the cooled cake. Dust with cocoa powder and serve.
This is what the result looked like…
from which you’ll agree that Mrs Crox makes a mean cake. It tasted great, too.
By now both of you’ll be asking why I’ve posted a cake recipe on what is essentially a science blog. But that’s the thing – there’s some
magic science magic going on here which, to me, initially defied understanding. We might very well know what went on a gnat’s crotchet after the Big Bang. We might even have a tolerable grasp of the behaviour of seven-transmembrane-helix G-protein-coupled-receptors. We can probably hack our way around the release of calcium from intracellular stores.
But what amazes me – and still does – is that you can make a cake, with bulk, and even a crumb structure, from little more than eggs beaten together and baked with sugar, butter and chocolate. Remember – there is no flour in this recipe.
What’s going on is clearly something very special at the mesocopic scale. Something which no doubt involves denatured albumen proteins, fats, sugary side-groups and colloids, and which Stephen and Athene might be better placed to explain than can I.
But wait, there’s more.
When I googled ‘science of cake’ the top hit was this explanation from
genius majority shareholder of Norwich City FC celebrity chef Delia Smith, which I quote here in extenso, and, what’s more, in full:
When fat and sugar are mixed together – the process is called creaming – little bubbles of air are being trapped in the mixture, each one surrounded by a film of fat (which is why the mixture changes colour during creaming as the trapped air creates a foam). It is this air which produces the lightness in the finished cake, but unless beaten egg is added to the mixture the fat would collapse and the air escape during cooking. The egg white conveniently forms a layer around each air bubble, and as the temperature of the cake rises in the heat of the oven this layer coagulates and forms a rigid wall round each bubble, preventing it from bursting and ruining the texture of the cake.
So, when we mix the cake, what we’re doing is introducing air into the mixture. The air is given shape by
lipids fats, just like soap bubbles, and these bubbles are trapped in matrix of protein which, on heating, denatures and becomes rigid.
Air is carried along on the rough surfaces of the sugar crystals. This is why we use caster sugar, as the smaller the crystals, the more air is incorporated. These bubbles of air are encased by a film of fat, creating a foam.
And here’s where the eggs come in:
Beaten egg is added to the mixture to stop the fat-coated air bubbles, created by creaming, from collapsing when heated. The egg proteins conveniently form a layer around each air bubble. As the temperature of the cake rises in the heat of the oven this layer coagulates to form a rigid wall around each bubble, preventing it from bursting and ruining the cake’s texture.
Connelly tells us – and this is important in the context of a flour-free cake – that eggs act as the raising agent, though they do require a lot of hard whisking, to introduce the bubbles. In regular cakes the raising agent in self-raising flour does the work for us, as well as providing a network of gluten to provide structure and shape. But, as I discovered, you can accomplish much the same without flour. It’s during the baking, though, that the egg proteins coagulate, trapping the bubbles (the gluten and starch help, if you have flour in your cake, but egg can do it on its own.)
Et voilà. A cake. Much of it provided by objects that come out of the back ends of chickens.
Thank you, Ladies!