This French onion soup, a simple and elegant staple of modern kitchens and restaurants everywhere, is easy to prepare and customize in presentation.
The soup itself dates back to the Romans but was modernized as soupe à l’oignon by the French in the eighteenth century. More recently, the dish was popularized in the 1960s by a rediscovery for contemporary home cooks, particularly by that great lover of French cuisine, Julia Child. This recipe is almost identical to hers (minus a flour roux) published in Mastering the Art of French Cooking, Vol. 1.
With simplicity comes greater importance on the details and preparation of each ingredient. Caramelizing the onions properly, over low heat for a very long time (careful not to scorch), will bring out their sugars and render them thoroughly. Yellow onions are used here but a variety of colors and types can be used for greater depth of flavor. Remember to cut the onions short enough to fit on a spoon else long, stringy rounds will make the soup messy for diners.
Likewise, a quality beef broth is required to fully enhance the caramelized onion flavor, although blends of beef and chicken stock are popular. A touch of fresh herbs would not be unwelcome, but compromises such as vegetable stock to make this dish vegan or skipping the alcohol added at the end will impact the full roundness of flavor, which relies upon the fat of the broth to carry the caramelized vegetable sugars.
A classic service for this dish is in an earthenware bowl or ramekin with a large crouton floated in it topped with cheese and fired (gratinéed) under a broiler for a few minutes to melt. Gruyère is the traditional choice as its nutty, smooth flavor plays well with the soup and melts beautifully for the complete, gooey presentation.
Otherwise, a simple garnish of grated Gruyère and a toasted baguette will suffice as a starter or a main course.
French Onion Soup
4 yellow onions
3 T butter
1 T olive oil
¼ t sugar
4 c beef broth
½ c white wine
1 T cognac
1 Thinly slice the onions and sauté in oil over medium heat, covered, for 15 min.
2 Add the sugar, butter and 1 t salt, and stir to combine. Continue to cook on low heat, uncovered, for about 45 min, stirring often to prevent scorching, until the onions are a deep golden brown.
3 Deglaze with the wine, scraping up any fond that might have formed. Add the broth and bring to a boil, then reduce the heat and simmer, covered, for 30 min.
5 Add the cognac just before serving. Season to taste.