A coral-pink shellfish sauce built on a béchamel finished with cream and whisked through with crayfish butter — butter into which the pounded shells of freshwater crayfish have given up their colour and aroma. Silky, rich and deeply marine with a faint sweetness, it is the classical sauce for pike quenelles and a luxurious coat for fish, eggs and shellfish. It is the defining derivative of the white mother sauce in the "à la Nantua" style, and any dish so named arrives under it.
The sauce is named for Nantua, a small town on its lake in the Bugey, in the Ain east of Lyon, where the local freshwater crayfish (écrevisses) were once so plentiful they became the district's emblem. By the late nineteenth century the sauce had entered the codified repertoire, and Escoffier records it in Le Guide Culinaire as a béchamel-based sauce reduced with cream and crayfish stock and finished with crayfish butter, garnished with the tails. It belongs to the broader "à la Nantua" garnish of crayfish tails and the sauce that bears the name, and it is bound up above all with the Lyonnais pike quenelle, the two having become a regional set-piece across the twentieth century. Wild French écrevisses are now scarce and largely protected, so most modern versions rely on farmed or imported crayfish.
Pour it and it runs a pale coral, glossy and clinging, smelling unmistakably of the sea even though its crayfish came from a lake. The taste is concentrated shellfish carried on cream — rich, rounded, gently sweet — with none of the iodine sharpness of a sea-shellfish sauce. Whole crayfish tails dropped in give little bursts of firm, sweet meat. Done well it is plush but not heavy; the faults are a sauce that tastes only of béchamel because the crayfish butter was weak, or one gone grainy from butter added too hot.
Two preparations meet. The base is a béchamel — a white roux of flour cooked in butter, whisked with milk so the starch swells and thickens it — reduced with cream for body. The flavour and colour come from crayfish butter: the shells, rich in the carotenoid pigment astaxanthin, are pounded and gently cooked in butter, which dissolves the fat-soluble pigment and aromatic compounds; the butter is then strained and chilled to set. Whisking this red butter into the warm sauce delivers a marine flavour and rose colour that no water-based stock could carry, because the key compounds are fat-soluble. The butter must go in off or barely on the heat: too hot and the emulsion breaks, leaving the sauce greasy and grainy.
Variations
Lobster or langoustine shells can stand in for crayfish to make a related shellfish butter and sauce. A little tomato purée and a splash of cognac are often added to deepen colour and aroma. The same sauce, lightened, naps eggs (œufs Nantua) and fillets of sole; thickened and enriched it coats the famous Lyonnais pike quenelles. Restaurants short of crayfish sometimes build the colour from a bought shellfish bisque or even a touch of paprika, a shortcut classicists frown on.
On the Palate
Where Sauce Nantua sits in the French flavor cloud
Ingredients
Serves 4
How it's made
6 steps · 45 min active + 15 min waiting
- 120 min
Pound or crush the crayfish shells, cook them gently in butter until deeply red and fragrant, then strain off the crayfish butter and chill it.
Watch outCook the crushed shells in butter only until deeply red and fragrant — the color and marine flavor are fat-soluble and lift into the butter, but scorch them and it turns bitter.
- 212 min
Make a white béchamel: cook flour in butter to a pale roux, then whisk in hot milk and simmer until smooth and thickened.
- 310 min
Reduce the béchamel with cream until it coats the back of a spoon.
- 45 min
Strain the sauce, return it to a clean pan, and bring it back to a gentle warmth off the boil.
- 58 min
Whisk in the chilled crayfish butter a little at a time until the sauce is smooth and rose-coloured; sharpen with a splash of cognac and season.
Watch outWhisk the chilled crayfish butter into the sauce off the boil, a little at a time — too hot and the butter splits instead of turning the sauce smooth and rose-colored.
- 65 min
Fold in reserved crayfish tails and spoon the sauce over quenelles, fish or eggs at once.
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