Sperovore, as it is spelt in A Life of Crime. However, it is spelled Speravore in the cast for The Diary of River Song: Series Two
Talk about it here.
Speravores were a squid-like species which fed off of potential. They had a unique existence in that they had a shared digestive tract, with all Speravores sharing the same meal when they ate, with the title of chef being a well-regarded one in their culture as the one responsible for choosing the best meals for their people. (AUDIO: A Life of Crime)