Tempering chocolate breaks down the fat, resulting in a hard, glossy chocolate.
Place the chopped chocolate in a heatproof bowl and sit it over a pan of water that has just boiled. Leave the chocolate to melt slowly off the heat The bowl must not touch the water at any time.
Stir the chocolate until it is smooth and reaches a temperature of 45°C (113°F).
Sit the bowl of melted chocolate over a large bowl filled with ice cubes. Stir until the temperature drops to 25°C (77°F).
Heat the chocolate again over the pan of hot water for 30-60 seconds, or until it reaches 32°C (90°F).