Plot: Michel Roux Jr sets out to discover the secret of chocolate - not just why we're addicted to this sublime and complex foodstuff, but its rich and varied history, from a sacred drink of Aztec emperors to the aphrodisiac of choice at the court of Louis XIV in Versailles. For Michel the best chocolate in the world is to be found in France, where the art of the chocolatier has been handed down from generation to generation