Can You Put Cognac in French Onion Soup?

Numerous classic French onion soup recipes include cognac, a brandy distilled from white wine in the French departments of Charente and Charente-Maritime. In fact, the soup can lack flavor and depth without it. What differs among the preparations is the stage at which the brandy is put in and the techniques used to bring the dish together. Simmered with the broth, added at the end or even flamed, cognac is an important ingredient in French onion soup.

Simmered

  • Cognac can be added early in the process of making French onion soup. Onions sautéed with butter are combined with flour in a “roux,” which acts as a thickening agent. Cognac and white wine are then used to “deglaze” it, dissolving the roux and scraping the flavors off the pot. Seasonings and beef stock are added and simmered gently for at least 20 minutes. The process cooks off the alcohol but the flavor remains.

Broiled

  • The onions fried in butter until golden, supplemented with flour and seasonings, can also be moistened with broth and water only, before simmering over moderate heat for 30 minutes. Cognac, along with Worcestershire sauce, is stirred into the cooked soup at the end. Soup is then poured in bowls, which are topped with slices of French bread and sprinkled with cheese, and placed under the broiler for a couple of minutes, just long enough to melt the cheese. This procedure results in a stronger-tasting soup, as most of the alcohol doesn’t evaporate.

Baked

  • In the Lyon-style onion soup favored by influential French chef Paul Bocuse, the water- or stock-based onion soup is first cooked without cognac. Separately, layers of toasted bread and slices of Gruyère cheese are piled up in a soup tureen in a manner reminiscent of lasagna. The tureen is topped up with onion soup and gratinated in the oven until complete absorption of the liquid. The rest of the onion soup is then added, along with half a glass of cognac, and baked for another 10 minutes prior to serving. In this method, the cheesy bread soaks up the soup and cognac instead of being placed on top at the end.

Flambéed

  • Cognac can also be flamed in the making of French onion soup. When stewing onions in butter, adding a little bit of sugar helps obtaining a desirable light-brown caramel color. Cognac is then poured in and lit up, which cooks away the alcohol but leaves behind a characteristic flambéed aroma. Beef or chicken stock and white wine complete the soup, which is served with cheese croutons on top or cheese toasts on the side.