Sauce Nantua
The science
Crayfish butter is made by pounding cooked crayfish shells with butter and gently melting, then straining: the shells' fat-soluble carotenoid pigment (astaxanthin) and shellfish flavor compounds dissolve into the butterfat, giving a coral-red, intensely shellfish-perfumed fat. Stirred into béchamel, it colors and flavors the sauce while the existing starch emulsion keeps the added fat suspended. Heat is what releases astaxanthin from its protein binding in the shell, which is why the shells must be cooked.
Flavor profile
Beurre d'écrevisse (crayfish butter) and cream, folded into béchamel, often finished with crayfish tails.
Culinary uses
The defining sauce of quenelles de brochet (pike dumplings) in Lyonnais cooking; also lobster and other shellfish preparations.
Reference notes
Parent: Béchamel. Region: Nantua, Bugey/Lyon. Technique: compound shellfish butters. Compare to the shellfish-driven sauce Normande in the Velouté family.