The sauce is often a mixture of egg yolks and brandy (such as Cognac), served with an oven-browned cheese crust, typically Gruyère.

The play took its name from a summer month in the French Republican Calendar, during which the Thermidorian Reaction in 1794 occurred, overthrowing Robespierre and ending the Reign of Terror.

[5] Maison Maire was a Parisian restaurant near the Théâtre de la Porte Saint-Martin.

The lobster Thermidor at Maison Maire was served like homard Américain, which was made with tomatoes, cayenne, and brandy, but with the addition of English mustard.

[2] An early London recipe for Homard à l'Américaine referred to à la Thermidor as a version with the addition of English mustard,[6] while an early American recipe for lobster Thermidor left out the tomatoes, cayenne, and mustard and added cream sauce thickened with Béarnaise sauce and a sprinkling of grated cheese.