Chocolate: the secrets every cook should learn

By John Campbell, owner and founder of The Woodspeen cookery school
Melting dark chocolate (couverture) to temper it might sound like a dark art, but these tips will help you to understand the science and mitigate the challenges of working with chocolate.

What is chocolate? 
In brief, cocoa beans are fermented, dried, then roasted to give cocoa nibs. These are roughly 50 per cent cocoa mass, 50 per cent cocoa butter. The former is dark and bitter – it’s what makes up cocoa powder. Cocoa butter is a pale fat with a melting point just below body temperature. When UK chocolate refers to its percentage of cocoa solids it means the combined quantity of cocoa mass and cocoa butter; the rest is mainly sugar (and milk for milk chocolate).

What is couverture?
It’s high quality chocolate with a higher cocoa butter content than baking or eating chocolate. It’s more finely milled for a smoother mouth-feel and has a minimum of 31 per cent cocoa butter – so it melts easily. It’s available at specialist suppliers and online (souschef.co.uk, amazon.co.uk). Dark, milk and white chocolate can all be tempered, but at different temperatures. 

What is tempering?
Good quality chocolate/couverture contains fatty crystals that melt and set at different temperatures. Tempering involves melting and setting the chocolate, in turn and at precise temperatures, to align the crystals so that when the chocolate is finally cooled and set, it has a shiny finish and a crisp snap. Heating/cooling too much, too quickly or in the wrong order results in fat crystals settling on the surface of the chocolate, which creates a whitish bloom.

Tips for tempering
It’s vital to start with quality chocolate. The higher the cocoa solids content, the faster the chocolate will melt, the easier it is to temper and the more stable it will be afterwards. But chocolate with a high cocoa solids content can also be quite bitter. Look at the percentages on the packaging.

Key things to avoid

Water causes chocolate to seize (turn lumpy and stiff). Why? Because the fat in the chocolate starts to form an emulsion with the water. If the chocolate siezes there’s no sure way of rescuing it, sadly – you need to start again using fresh chocolate. So… Keep everything dry, with a cloth to hand to wipe the base of the bowl in which you’re melting the chocolate, once you remove it from the heat. Use a rubber spatula to stir – wooden spoons can harbour flavours, grease and water.

Too much heat. High temperatures (over 50°C) can also cause chocolate to seize, plus it may taste burnt. White chocolate/couverture is particularly prone to burning. Use an accurate instant-read digital probe thermometer to test the chocolate – you need one that’s quick to react.

Humidity will give the chocolate a white mottled bloom. Moisture in the atmosphere interferes with crystal formation and leaves a powdery sheen over the chocolate’s surface. A cool, well ventilated but draft-free room is ideal for tempering.

Rapid temperature change will also cause a bloom on the surface of the chocolate. Bloom doesn’t affect the taste of the chocolate, just the appearance, dulling it down and affecting the shine. Allow the chocolate to set fully before storing or unmoulding – depending on your surroundings and the size of the item this can range from 10 minutes to a few hours for a large chocolate egg. The more successfully you’ve tempered the chocolate, the quicker it will be to set. Once cooled, the tempered chocolate is best stored at around 20°C in a sealed container, out of direct sunlight and not in the fridge.

The Woodspeen is a Michelin-starred restaurant and cookery school in Newbury, Berkshire. John has written several cookery technique manuals and newspaper articles and has appeared on the BBC’s Saturday Kitchen and MasterChef programmes.