Classic French Onion Soup
A deeply savory and comforting classic French soup featuring slow-caramelized yellow onions in a rich beef broth, finished with a splash of sherry and topped with a toasted baguette crust smothered in bubbly, golden Gruyère cheese.
Equipment
- Heavy-bottomed pot or Dutch oven
- Oven-safe soup bowls (crocks)
- Cutting board
- Chef's knife
- Ladle
- Baking sheet
Ingredients
Soup Base
- 3 lbs yellow onions — peeled and sliced 1/4-inch thick pole-to-pole
- 3 tablespoons unsalted butter
- 1 tablespoon olive oil
- 1 teaspoon kosher salt — plus more to taste
- 0.5 teaspoon granulated sugar (optional) — helps with caramelization
- 2 cloves garlic — minced
- 2 tablespoons all-purpose flour
Liquids & Aromatics
- 0.5 cups dry sherry — can substitute dry white wine or cognac
- 6 cups high-quality beef broth — or beef stock
- 3 sprigs fresh thyme — tied together
- 1 leaf bay leaf
- 0.5 teaspoon black pepper — freshly ground
Topping
- 1 loaf French baguette — cut into 1-inch thick slices
- 8 ounces Gruyère cheese — freshly grated
Soup Base
| 3 lbs | yellow onions | peeled and sliced 1/4-inch thick pole-to-pole |
| 3 tablespoons | unsalted butter | |
| 1 tablespoon | olive oil | |
| 1 teaspoon | kosher salt | plus more to taste |
| 0.5 teaspoon | granulated sugar (opt.) | helps with caramelization |
| 2 cloves | garlic | minced |
| 2 tablespoons | all-purpose flour |
Liquids & Aromatics
| 0.5 cups | dry sherry | can substitute dry white wine or cognac |
| 6 cups | high-quality beef broth | or beef stock |
| 3 sprigs | fresh thyme | tied together |
| 1 leaf | bay leaf | |
| 0.5 teaspoon | black pepper | freshly ground |
Topping
| 1 loaf | French baguette | cut into 1-inch thick slices |
| 8 ounces | Gruyère cheese | freshly grated |
Instructions
-
Melt the butter and olive oil in a large heavy-bottomed pot or Dutch oven over medium heat. Add the sliced onions, salt, and sugar. Toss to coat the onions in the fat.
~5 minSlicing onions pole-to-pole (root to stem) helps them hold their shape better during the long cooking process. -
Cook the onions, stirring occasionally, until they reduce in volume, soften, and develop a deep mahogany color. If the bottom of the pot gets too dark, add a splash of water and scrape up the browned bits.
~45 minPatience is key here. True caramelization takes 40-50 minutes. Do not rush this step by turning up the heat, or the onions will burn rather than sweeten. -
Once the onions are deeply caramelized, add the minced garlic and cook for 1 minute until fragrant. Sprinkle the flour over the onions and cook, stirring constantly, for 2 minutes to cook out the raw flour taste.
~3 min -
Pour in the dry sherry to deglaze the pot, scraping up any fond (browned bits) stuck to the bottom. Cook until the sherry has mostly evaporated.
~2 min -
Stir in the beef broth, thyme sprigs, bay leaf, and black pepper. Bring the soup to a boil, then reduce the heat to low, cover partially, and let simmer to meld the flavors.
~20 minTaste the soup near the end of the simmer and adjust salt and pepper if needed. Remove the thyme sprigs and bay leaf before serving. -
While the soup simmers, preheat the oven to 400°F (200°C). Arrange the baguette slices on a baking sheet and toast for 5-7 minutes until dry and lightly golden. Remove from the oven and switch the oven setting to Broil.
~7 minYou can rub the toasted bread with a halved clove of raw garlic for extra flavor. -
Place 4 oven-safe soup crocks on a sturdy baking sheet. Ladle the hot soup into the bowls, leaving about an inch of space at the top. Top each bowl with 1-2 slices of toasted baguette, then generously pile the grated Gruyère cheese over the bread and up to the edges of the bowls.
~3 minLetting the cheese overlap the rim slightly creates those irresistible crispy, burnt cheese edges. -
Carefully transfer the baking sheet with the bowls to the oven. Broil for 3-5 minutes, watching closely, until the cheese is bubbling, melted, and golden brown in spots. Let sit for 5 minutes before serving (it will be extremely hot).
~5 minKeep the oven door slightly ajar if your broiler runs very hot so you can monitor the cheese.
Tips & Storage
- Always use block Gruyère and grate it yourself; pre-shredded cheese contains anti-caking agents that prevent it from melting smoothly.
- If you don't have oven-safe bowls, you can make Gruyère toasts on a baking sheet and simply float them on top of the hot soup right before serving.
- A mix of beef and chicken stock can be used if you prefer a slightly lighter flavor.
- Storage: Store the soup and the toasted bread separately. Keep the soup in an airtight container in the refrigerator for up to 4 days. Reheat the soup on the stovetop, then assemble with fresh bread and cheese and broil before serving.