Sauce américaine is the most dramatic sauce in the French repertoire — built live from a lobster dispatched, cut, sautéed, flambéed, and simmered into its own sauce in a single unbroken sequence. The lobster is killed with a knife through the cross on the head, split, cleaned (reserving the coral and tomalley), and the tail and claws cut into sections through the shell. These pieces are sautéed in blazing-hot olive oil and butter until the shells turn scarlet — the carotenoid pigment astaxanthin, released from its protein bond by heat, provides the sauce's legendary coral colour. Cognac is added and flambéed, then shallots, garlic, white wine, fish stock, tomato concassée, and a bouquet garni are added. The sauce simmers for 20 minutes while the lobster finishes cooking. The meat is removed and reserved for service. The sauce is reduced, then the reserved coral and tomalley — pounded with soft butter to form beurre de homard — are whisked in off heat. This compound enriches the sauce with an intensity of lobster flavour that no stock alone can achieve. The sauce is strained through a chinois, and a chiffonade of tarragon is added at the final moment. The result is a sauce of staggering depth: crustacean sweetness, tomato acid, cognac warmth, and the mineral-rich complexity of the coral butter. Despite its name, sauce américaine is entirely French — likely a corruption of 'armoricaine' (from Armorica, the ancient name for Brittany), though this etymology is disputed. It is the canonical sauce for lobster Thermidor and homard à l'américaine.
Kill, section, and sauté the lobster — the sauce builds from the living animal. Flambé cognac to burn alcohol and caramelise crustacean sugars. Reserve coral and tomalley for beurre de homard — this is the sauce's soul. Strain through chinois for silk. Tarragon added at the very end.
The lobster must be alive for the sauce — the freshness of the juices and the fond created during the shell sauté are the entire point. If the coral is unavailable (male lobsters have less), supplement with a tablespoon of tomato paste sautéed in the pan for colour. For the most refined texture, blend the strained sauce briefly then pass through muslin — this creates an almost bisque-like smoothness.
Using pre-cooked lobster — the shell sauté and the fond it creates are essential flavour steps. Skipping the coral butter — without it, the sauce is merely a good fish sauce, not américaine. Over-reducing — the sauce turns bitter from concentrated tomato and carotenoid compounds. Using dried tarragon — the fresh herb's anise note is irreplaceable.
Escoffier, Le Guide Culinaire; Larousse Gastronomique