Tempering chocolate, step by step

1. Chop 300g of couverture finely and set aside a third of it. 2. Melt the other two-thirds to 45–50°C for dark, 45°C for milk or white. Take it fully to temperature — this erases every existing crystal, and stopping short is the commonest invisible cause of failure. 3. Off the heat, add the reserved third a handful at a time, stirring until each addition dissolves. 4. Stop adding when the chocolate reaches 31–32°C for dark, 30–31°C milk, 29–30°C white. 5. Dip a strip of baking paper, set it aside at cool room temperature, and check after three to five minutes. 6. If it is glossy, streak-free and snaps cleanly, work. If not, remelt and start again.

Not melting hot enough at step 2. Chocolate that merely looks melted — around 40°C — retains stable crystal fragments that compete with the seed, and the result is unpredictable in a way nothing about the visible process explains.

And a warm room. Setting needs an ambient temperature below about 20°C, and below 18°C for milk and white. A correctly tempered batch in a 26°C kitchen will not set, and the test strip will give a false negative.

Below about 200g, chocolate cools faster than you can work it, and the batch drifts out of the working window before you have used it.

Temper more than you need. The surplus sets, keeps indefinitely, and can be re-tempered — nothing is wasted by making too much, and a great deal of time is wasted by making too little.