Nantua sauce
Nantua sauce is a classical French sauce consisting of: It is named for the town of Nantua, which is known for its crayfish, and the term à la Nantua is used in classical French cuisine for dishes containing crayfish. Sauce Nantua is the classic accompaniment to quenelles de brochet (pike dumplings), making quenelles Nantua.
Source: Wikipedia