A cake in the shape of Deanna Troi, served with mint frosting in one of Data's disturbing dreams, which proved to be a clue to invisible parasites feeding on the crew.
The cellular peptide cake appears in the Next Generation episode Phantasms. Data's dream programme begins producing nightmares, and in one of them he finds Troi laid out on a table in Ten Forward as a cake, which Worf is cheerfully eating and recommends for its mint frosting.
The images disturb Data so much that, while awake, he stabs Troi in the shoulder. Working through the dreams on the holodeck with a simulated Sigmund Freud and then with Picard and La Forge, he realises that they are his subconscious trying to warn him.
Interphasic organisms, undetectable to the crew, are attached to their bodies and extracting their cellular peptides. At the end Troi presents Data with a cake made in his own likeness.