Nantua sauce
Nantua sauce is a classical French sauce consisting of a béchamel sauce base, cream, and crayfish butter, along with crayfish tails.
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, making quenelles Nantua.