French Onion Soup

I learned how to make this French onion soup recipe while working at a French restaurant known for the dish, and the most important lesson was not to rush the onions. Cooking them slowly until deeply golden and almost jammy gives the soup its signature sweetness and depth of flavor.

A few other touches make a difference: a little flour gives the broth some body, sherry adds depth, and a combination of Gruyère and Parmigiano-Reggiano makes for an especially flavorful topping. It takes some time, but most of it is hands-off—and the result is every bit as satisfying as the French onion soup you’d order at a good restaurant.

What You’ll Need To Make French Onion Soup

• Sweet onions: The star of the soup. Sweet onions caramelize beautifully, becoming deeply golden and almost jammy as they cook. Yellow onions will also work well.
• Butter & olive oil: Used together to slowly caramelize the onions, adding richness while helping them cook evenly.
• Flour: Just a small amount gives the broth a little body without making it thick or gravy-like.
• White wine & dry sherry: Add acidity and depth and help loosen the flavorful browned bits from the bottom of the pot. There’s no need to splurge on an expensive wine, but use a dry white you’d enjoy drinking. For the sherry, choose a dry drinking sherry rather than cooking sherry.
• Beef broth & Worcestershire sauce: Create the savory backbone of the soup. Worcestershire adds an extra layer of umami without calling attention to itself.
• Thyme & bay leaves: Add subtle herbal flavor as the soup simmers.
• Baguette: Toasted slices soak up some of the broth while providing a sturdy base for all that melted cheese.
• Gruyère & Parmigiano-Reggiano: Gruyère melts beautifully and has the nutty flavor traditionally associated with French onion soup; Parmigiano-Reggiano adds a salty, savory finish.
• Jump to the printable recipe for precise measurements

How To Make French Onion Soup

Caramelize the onions: This is the step you don’t want to rush. Cook the onions slowly until deeply golden, soft, and almost jammy. Stir occasionally at first, then more often as they darken, scraping up the flavorful browned bits from the bottom of the pot. If they brown too quickly, add a splash of water to loosen the fond and keep it from burning.

Deglaze and simmer the soup: Pour in the wine and scrape up all that flavorful fond, then let it cook down until the onions are jammy again. Stir in the flour, followed by the broth, Worcestershire, and herbs, and let the soup simmer until the flavors come together. The sherry goes in at the end to deepen the broth.

Toast the baguette: While the soup simmers, toast the baguette slices until they’re dry, crisp, and golden around the edges. You want them nice and sturdy so they can soak up some broth without completely falling apart.

Assemble and broil: Ladle the hot soup into oven-safe crocks, top with the toasted baguette, and pile on the Gruyère and Parmigiano-Reggiano. Broil until the cheese is melted, bubbling, and browned around the edges. Give the crocks a few minutes to cool before digging in—they’ll be very hot.