Classic French Onion Soup

The whole dish rides on one step: caramelizing a mountain of onions low and slow until they collapse into a deep amber jam — there's no shortcut worth taking here.

Instructions

1. 1

   Melt the butter with the olive oil in a large, heavy-bottomed pot or Dutch oven over medium heat.

2. 2

   Add the sliced onions, salt, and sugar (the sugar helps caramelization along, the salt draws out moisture). Stir to coat.

3. 3

   Cook, stirring every 5–10 minutes, for 45–60 minutes total. The onions will first release liquid and soften, then gradually shrink and turn golden, then deep amber-brown. Lower the heat if they start to catch or blacken in spots — true caramelization is slow and cannot be rushed with high heat.

4. 4

   Add the garlic and cook 1 minute more, until fragrant.

5. 5

   Pour in the wine, scraping up any browned bits stuck to the bottom of the pot with a wooden spoon. Simmer until the wine has mostly evaporated, 3–4 minutes.

6. 6

   Sprinkle the flour over the onions and stir constantly for 1–2 minutes to cook off the raw flour taste and form a light roux with the fond.

7. 7

   Gradually pour in the beef broth and chicken broth, stirring as you go to prevent lumps. Add the thyme and bay leaf.

8. 8

   Bring to a simmer, then reduce heat to low and cook uncovered for 30 minutes, allowing the flavors to meld. Season with salt and pepper to taste; remove the bay leaf and thyme sprigs.

9. 9

   Meanwhile, toast the baguette slices under the broiler or in a 400°F oven until golden and crisp, about 5 minutes.

10. 10

    Preheat the broiler. Ladle the hot soup into oven-safe crocks set on a baking sheet. Float 1–2 toasted baguette slices on top of each and pile generously with Gruyère.

11. 11

    Broil until the cheese is melted, bubbling, and browned in spots, 2–4 minutes — watch closely, as broilers vary widely. Let cool slightly before serving, as the crocks and soup will be extremely hot.