French Onion Soup with Gruyère Recipe
Slowly caramelizing the onions over low heat for close to an hour builds the deep, sweet-savory base that makes this soup worth the wait, and Gruyère melts into a stretchy, nutty crust under the broiler without turning greasy or rubbery the way milder cheeses can.
- Prep
- 15 min
- Cook
- 1 hr 15 min
- Total
- 1 hr 30 min
- Servings
- 6
Ingredients
- 3 lbs yellow onions, thinly sliced
- 4 tbsp unsalted butter
- 1 tbsp olive oil
- 1 tsp kosher salt
- 1/2 tsp granulated sugar
- 2 tbsp all-purpose flour
- 1/4 cup dry sherry
- 8 cups beef broth
- 4 sprigs fresh thyme sprigs
- 1 leaf bay leaf
- 12 slices baguette, sliced into 1-inch rounds
- 8 oz Gruyère cheese, grated
Nutrition per serving
- Calories
- 525
- Protein
- 21g
- Carbs
- 55g
- Fat
- 24g
Based on the recipe as written, one serving. Recalculates if you swap an ingredient above. An estimate only, exact values depend on the specific ingredients used.
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Instructions
- 1Melt the butter with the olive oil in a large heavy pot over medium-low heat. Add the sliced onions, salt, and sugar, and stir to coat.
- 2Cook the onions, stirring every 5 to 8 minutes and scraping up any browned bits from the bottom of the pot, for 45 to 55 minutes, until deeply golden brown and jammy. Lower the heat if they start to darken too fast or stick.
- 3Sprinkle the flour over the onions and stir constantly for 1 minute to cook off the raw flour taste.
- 4Pour in the sherry and scrape up any remaining browned bits, letting it bubble and reduce by about half, roughly 2 minutes.
- 5Add the beef broth, thyme sprigs, and bay leaf. Bring to a simmer, then reduce the heat and cook uncovered for 20 minutes to let the flavors meld. Remove the thyme sprigs and bay leaf, and season with additional salt to taste.
- 6While the soup simmers, arrange the baguette slices on a baking sheet and broil for 1 to 2 minutes per side, until lightly toasted.
- 7Position an oven rack about 6 inches from the broiler and preheat the broiler. Ladle the hot soup into broiler-safe crocks set on a rimmed baking sheet.
- 8Float 1 to 2 toasted baguette slices on top of each bowl of soup, then pile grated Gruyère generously over the bread and slightly over the edges of the crock.
- 9Broil for 2 to 4 minutes, watching closely, until the cheese is melted, bubbling, and browned in spots. Let cool for a few minutes before serving, since the crocks and cheese stay very hot.
Tips & variations
- If broiler-safe crocks aren't available, melt the cheese-topped croutons separately on a baking sheet and float them on top of the soup after ladling, since not all bowls can handle direct broiler heat.
- Comté or a mix of Gruyère and sharp white cheddar both work as substitutes if Gruyère isn't available, though the flavor will be milder.
- A splash of dry white wine or brandy can replace the sherry for a slightly different depth of flavor.
- For a vegetarian version, swap the beef broth for a well-seasoned mushroom or dark vegetable stock.
Storage & reheating
Store the soup base (without the bread and cheese) in an airtight container in the refrigerator for up to 4 days, or freeze for up to 3 months. Reheat gently on the stovetop, then ladle into broiler-safe crocks and top fresh with toasted bread and cheese before broiling, since previously broiled cheese won't reheat well.
Tips from the Tulo kitchen
- Slicing all the onions before starting keeps the caramelizing step moving, since there's no good stopping point once the onions hit the pot.
- A wide, heavy-bottomed pot caramelizes onions faster and more evenly than a narrow one, because more surface area touches the heat.
FAQ
Why is Gruyère the classic cheese for French onion soup?
Gruyère has a low moisture content and a high proportion of fat to protein, which lets it melt into long, smooth strands and brown under a broiler instead of turning oily or separating like softer cheeses can.
Can I make French onion soup ahead of time?
Yes. The onion and broth base actually improves after a day or two in the refrigerator as the flavors continue to meld. Add the bread and cheese fresh right before broiling and serving.
What can I use instead of broiler-safe crocks?
Toast the bread and melt the cheese on a separate baking sheet under the broiler, then slide the cheese-topped crouton onto the surface of the hot soup in a regular bowl.
Why did my onions turn out steamed instead of caramelized?
This usually happens when the pot is overcrowded or the heat is too high, which causes the onions to release liquid faster than it can evaporate. Use a wide pot and keep the heat at medium-low, stirring occasionally rather than constantly.
