Deeply caramelized onions and a balanced, flavorful broth come together in this classic French onion soup, finished with crisp baguette and melted Gruyère.
2quarts chicken stock (preferably homemade or high-quality store-bought)
2 cloves garlic, minced
2–3 sprigs fresh thyme
1 bay leaf
1 teaspoon fish sauce (optional but recommended)
1/2 teaspoon apple cider vinegar
Bread & Cheese
1 baguette, sliced (see instructions for two preparations)
8–12ounces Gruyère cheese, grated
Optional: a small amount of Parmesan cheese (for browning)
Garnish
Fresh chives and/or green onions, finely sliced
Instructions
Cook the onions in butter — Melt the butter over medium heat in a large, heavy-bottomed pot. Add the onions, season lightly with salt, and cook, stirring occasionally, until they soften and release their moisture.
Caramelize the onions slowly, managing the fond — Reduce heat to medium-low and continue cooking, stirring periodically. When the bottom of the pot begins to look dry and browned, deglaze with a small splash of water or dry white wine—just enough to loosen the fond and fold it back into the onions without flooding the pan. Continue this process until the onions are deeply golden, soft, and cohesive.
Add garlic and deglaze with wine — Stir in the minced garlic and cook briefly until fragrant. Add a final splash of white wine and cook until mostly reduced.
Build the broth — Add the chicken stock, thyme, bay leaf, and fish sauce (if using). Bring to a gentle simmer and cook for 20–30 minutes to allow the flavors to come together. While the soup simmers, prepare the bread.
Prepare the crouton base — Place half of the baguette slices on a baking sheet and bake at 325°F until fully dried and lightly golden, about 15–20 minutes. These should be crisp throughout and able to absorb broth without becoming mushy.
Prepare the top slices — Toast the remaining baguette slices at 375–400°F until well browned on the surface but still slightly tender in the center. Set aside for assembly.
Finish the soup — Remove the thyme stems and bay leaf. Taste and adjust seasoning with salt and pepper. Stir in the apple cider vinegar to brighten the broth.
Assemble the bowls — Ladle hot soup into oven-safe bowls. Place a crouton in each bowl. Add a small layer of caramelized onions (with minimal broth) over the crouton. Top with a toasted baguette slice.
Add cheese and broil — Cover the top with grated Gruyère (and a small amount of Parmesan, if using). Broil until the cheese is melted, bubbling, and lightly browned.
Finish and serve — Garnish with chives or green onions and then serve immediately.