Drawn together: the conching machine

Categories: Behind the stalls

Award-winning blogger and Borough Market regular Ed Smith displays a talent for illustration as well as the written word, as he talks to stallholders about the tools of their trade. This month: the conching machine

Words and illustration: Ed Smith 

Louise Anderson, Rabot Estate

I have been working with chocolate for about five and a half years now. For the last three years I’ve been resident chocolatier at Rabot in Borough Market, which is also how long we’ve been open as a cafe and restaurant here on Bedale Street.

We make small batch chocolate on site every week, mostly using the beans from our plantation in Saint Lucia, although from time to time we get special guest cocoa beans in too. With the beans from Saint Lucia we control every aspect of chocolate making, literally from tree, to bean, to bar. I think you get a better product this way.

As a chocolatier, I want to see and control every step. When you do that, you can ensure that each of the steps are right for the particular bean, and therefore right for the result we’re trying to achieve.

A chocolate fondue fountain
A really important stage in the chocolate-making process is called ‘conching’. We have a conching machine in the shop, you can see it by the counter—it’s almost always running. It looks as though it is just a vat of melted chocolate, perhaps spinning for effect like a chocolate fondue fountain, but actually it’s vital to the chocolate-making process.

Before we go into more detail about that, I will quickly say what the other chocolate-making stages are. First, when the dry beans arrive at Borough, they are roasted. We have a special roasting machine which is actually technically a German coffee roaster. Then we have to ‘winnow’ the roasted beans, which basically means crushing the beans and removing the roasted shells to expose the cacao nibs. We do this by hand.

Now comes the conching stage. This is when the cacao nibs are ground by three granite wheels. There’s a large one at the base of the machine, which sits flat and spins round. On top of that there are two smaller granite wheels, which are stood at right angles to the first and spin on a perpendicular axis.

Rabot conching machine

Tough and abrasive
The nibs are pretty tough and abrasive, which is why the wheels are granite, and the friction caused by the conching process generates a lot of heat, hence the ground nibs melt and the machine looks like it’s simply spinning melted chocolate!

The longer you conch for, the more acidity and bitterness is lifted off the beans, and the smoother, more complex the result. When you’re aiming for a dark chocolate, with a high cocoa percentage, that means there’s less (or no) sugar and milk powder added, so it takes longer to ensure the product will have an enjoyably smooth mouthfeel and won’t be too bitter or tanniny. The 70 per cent chocolate that’s in there at the moment will be conched for 49 hours.

When the time is up, the chocolate (technically ‘couverture’ at this stage) is poured out into blocks, and these are left at a cool temperature to develop more flavour for a couple of months. From those blocks we create our products.

Shiny, glossy chocolate
If the couverture is going to be used as a bar or as coating, it needs to be ‘tempered’, which is a heating and cooling process that results in shiny, glossy chocolate that has the enjoyable snap and bite that we all crave. I use another machine to temper the dark chocolates, but I temper milk and white chocolates by hand.

Even though I work with it every day, I still enjoy eating chocolate—you need to test, don’t you?!—and I love watching the conching machine. It’s so mesmerising. I love the fact that everything we make in-house has to go through it. Our conching machine is central to what we do.