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A cozy, comforting, classic recipe for French Onion Soup with caramelized onions in rich deep broth topped with toasty croutons and melted gruyere.  Vegan and Vegetarian Adaptable! #frenchonionsoup

French Onion Soup

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  • Author: Sylvia Fountaine | Feasting at Home
  • Prep Time: 15
  • Cook Time: 75
  • Total Time: 1 hour 30 minutes
  • Yield: 4-6 1x
  • Category: soup
  • Method: stovetop
  • Cuisine: French
  • Diet: Vegetarian


A cozy, comforting, classic recipe for French Onion Soup with caramelized onions in rich deep broth topped with toasty croutons and melted gruyere.  Vegan and Vegetarian Adaptable!


Units Scale
  • 6 large yellow onions
  • 2 tablespoons olive oil
  • 2 tablespoons butter ( or sub olive oil)
  • 1 1/2 teaspoons salt
  • 1 tablespoon fresh thyme (or 1 teaspoon dried)
  • 2 teaspoons flour (or leave it out)
  • 6 cups beef stock or veggie broth (see notes)
  • 1/2 teaspoon pepper, more to taste
  • 2 bay leaves
  • 1/4 teaspoon sherry vinegar, or red wine vinegar (or see notes)
  • ——–
  • One baguette
  • 6 ounces Gruyere, Comtéor Emmental cheese (or sub melty vegan cheese), sliced
  • a few sprigs fresh thyme for garnish


Preheat the oven to 350F

Slice the ends off the onions, cut in half lengthwise, through the stem, and peel.  Slice in the direction of the stem to root (with the lines, rather than cross-grain) into 1/4 inch thick slices. Slicing with the lines with the grain helps the onions soften (thanks, Thomas Keller). You should have about 12-13 cups (just over 3 quarts) of sliced onions.

Heat the butter and olive oil in a heavy bottom pot or dutch oven over medium heat, coating the bottom. Add the onions and toss with the salt. Cover for 3-4 minutes. Uncover, stir and let cook for 45 minutes, stirring every ten minutes, taking care to get all the corners, reducing the heat to medium-low halfway through.

While the onions are cooking toast the bread. Slice the baguette (2 slices per person) into 3/8 inch slices, brush or spray with olive oil and sprinkle with salt. Place in the oven either on a sheet pan or directly on the rack and toast for 10 minutes, then turn over, toast another 10 minutes until crisp. Set aside.

Once onions begin to look caramel in color add the thyme. Increase heat to med or medium-high, and stir fairly constantly for  5-10 more minutes, until deeply golden. (You could do this ahead to this point and refrigerate.)

Sprinkle the flour over the warm caramelized onions, stirring and toasting it for 1 minute. Add the broth, bay leaves and pepper. Stir, scraping up any browned bits and bring to a boil, then lower heat and simmer uncovered for 10-15 more minutes.

Add the 1/4 teaspoon vinegar. Taste. Adjust salt and pepper- and if too salty for your taste, add a splash of water to dilute. Remove the bay leaves.

If serving traditionally, in a ramekin, set oven to broil (or heat to 475F). Ladle the soup, 1/2 inch from the rim. Top the warm soup with 2 toasted baguette slices slightly layered (do not sink them in, try to keep them afloat!) cover with sliced cheese, place on a sheet pan, repeat with the others and place sheet pan in the hot oven, baking until golden and bubbling. If broiling, keep a careful eye on them.

Garnish with a sprig of thyme and serve immediately!



DEGLAZE: Yes of course; instead of vinegar,  you can deglaze the caramelized onions with a splash of sherry or white wine, cook this off a bit before adding the flour. You can also add a tablespoon or two of sherry wine ( not vinegar) or port to the simmering soup.

Soup can be made ahead and reheated. Croutons can be made ahead.

Some French folk, like to add a couple of cloves of garlic.

Vegan Version: Use all olive oil, sub veggie broth or Onion Boullion. At the end, add a small splash of soy sauce or miso paste to add depth- add this to taste. Leave the cheese off, just add the olive-oil toasted croutons or add vegan cheese.

This recipe makes 4 hearty dinner-sized portions or 6 smaller portions – yields 7- 7-1/2 cups total.

Tip: If you don’t have oven-proof ramekins, melt the cheese over the croutons under a broiler, serve the soup in bowls and top with the melty golden croutons.


  • Serving Size: 1 ¼ cup
  • Calories: 378
  • Sugar: 8.8 g
  • Sodium: 1470.5 mg
  • Fat: 18.7 g
  • Saturated Fat: 8.7 g
  • Carbohydrates: 35.6 g
  • Fiber: 3.6 g
  • Protein: 18.7 g
  • Cholesterol: 41.4 mg