This Book is Not Good for You: Book 3 (Secret 3) (The Secret Series)

Cass, Max-Ernest and Yo-Yoji, members of the top-secret Terces Society, are on a mission to track down a cursed Aztec tuning fork that has the power to recreate any flavour its user has ever tasted. But when an evil chef uses the fork to create a deadly chocolate recipe, and tricks Cass and Yo-Yoji into eating it, only Max-Ernest can save the day.