French onion soup is a classic comfort food known for its rich, savory broth, sweet caramelized onions, and a bubbling crown of melted cheese atop toasted bread. While it’s now a staple in French restaurants and home kitchens worldwide, its roots are humble and steeped in centuries of history.
The Origins of French Onion Soup
French onion soup traces its origins back to ancient times, with versions of onion soup enjoyed as far back as the Roman Empire. Onions were cheap, plentiful, and easy to store, making them a staple for the poor across Europe. The modern version as we know it today—made with caramelized onions, beef broth, and gratinéed with cheese—emerged in Paris in the 18th century. It became popular in the bustling markets of Les Halles, where it was served as a restorative meal for workers and late-night revelers alike. Over time, the soup’s reputation grew, and it became a beloved dish throughout France and beyond.
Ingredients for Classic French Onion Soup
4 large yellow or sweet onions, thinly sliced
3 tablespoons unsalted butter
1 tablespoon olive oil
1 teaspoon sugar
2 cloves garlic, minced
1 cup dry white or red wine (optional)
8 cups beef broth
2–3 sprigs fresh thyme (or 1 teaspoon dried thyme)
1–2 bay leaves
Salt and black pepper to taste
1 baguette, sliced
2 cups grated Gruyère cheese (or Comté/Swiss cheese)
Optional: Worcestershire sauce, sherry, or balsamic vinegar for extra depth
Step-by-Step: How to Make French Onion Soup
Caramelize the Onions:
In a large heavy-bottomed pot, melt butter with olive oil over medium-low heat. Add the sliced onions and sugar, stirring occasionally. Cook gently for 40–60 minutes, until the onions are deep golden brown and caramelized—this step is key for the soup’s signature sweetness and depth.
Deglaze the Pot:
Add the garlic and cook for a minute. Pour in the wine (if using), scraping up the browned bits from the bottom of the pot. Simmer until the wine is mostly reduced.
Build the Broth:
Add the beef broth, thyme, bay leaves, and a splash of Worcestershire sauce or sherry if desired. Bring to a boil, then reduce heat and simmer uncovered for 30–60 minutes to develop flavor. Season with salt and pepper.
Prepare the Bread:
While the soup simmers, toast the baguette slices until golden. For extra flavor, rub them with a cut clove of garlic.
Assemble and Broil:
Ladle the soup into oven-safe bowls. Top each with toasted bread and a generous handful of grated Gruyère cheese. Place the bowls under a broiler until the cheese is melted, bubbly, and golden brown.
Serve:
Carefully remove from the oven and serve hot, garnished with extra thyme if desired.
Why French Onion Soup Endures
French onion soup’s enduring popularity comes from its perfect balance of sweet, savory, and umami flavors, combined with the irresistible texture of gooey cheese and crisp bread. From its humble beginnings as peasant food to its place as a French culinary icon, this soup proves that simple ingredients, when treated with care and patience, can create something truly extraordinary.
