The cause of action requires a showing that (1) the defendant was enriched, (2) at the expense of the plaintiff, and (3) that it would be inequitable to permit the defendant to retain that which is claimed by the plaintiff.
Student note: The essential inquiry in any action for unjust enrichment or restitution is whether it is against equity and good conscience to permit the defendant to retain what the plaintiff seeks to recover.
Case: Demetriades v. Kalpakis, NY Slip Op 08349 (2d Dep't November 29, 2017)
Here is the decision.