About this recipe

A timeless bistro classic made right in your own kitchen. Deeply caramelized onions simmered in rich beef broth with a splash of white wine and fresh thyme, ladled into crocks and crowned with crusty toasted baguette slices and a blanket of bubbling, golden Gruyère cheese. This recipe takes patience — but the results are absolutely worth every minute.

Instructions

1. 1

   Melt the butter with the olive oil in a large Dutch oven or heavy-bottomed pot over ^[medium heat]. Add all the sliced yellow onions, kosher salt, and granulated sugar. Stir to coat well. Cook uncovered, stirring every 5–8 minutes, for 50–60 minutes total. The onions should slowly turn deep golden-brown and jammy. If they're browning too fast or sticking, lower the heat and add a splash of water to deglaze. Don't rush this step — properly caramelized onions are the soul of this soup.

2. 2

   Add the garlic minced and cook, stirring, for 1 minute until fragrant.

3. 3

   Pour in the white wine and stir, scraping up any browned bits from the bottom of the pot. Let the wine cook down for about 3 minutes until mostly evaporated.

4. 4

   Sprinkle the all-purpose flour over the onions and stir well to coat. Cook for 2 minutes, stirring constantly, to eliminate the raw flour taste.

5. 5

   Gradually pour in the beef broth and water, stirring constantly. Add the thyme sprigs, bay leaves, Worcestershire sauce, and black pepper. Bring to a boil, then reduce heat to ^[low]. Simmer uncovered for 20–25 minutes. Remove the thyme sprigs and bay leaves. Taste and adjust kosher salt and black pepper as needed.

6. 6

   While the soup simmers, preheat your oven to ![400°F]. Arrange the baguette slices on a baking sheet and brush both sides lightly with olive oil. Bake for 6–8 minutes, flipping once halfway through, until golden and crisp. Set aside.

7. 7

   Grate the Gruyère (and Parmesan cheese if using) and set aside. Have your oven-safe soup crocks ready on a sturdy baking sheet.

8. 8

   Switch your oven to the broiler setting (^[high]). Ladle the hot soup into the oven-safe crocks, filling them about 3/4 full. Place 1–2 toasted baguette slices on top of each crock, slightly overlapping if needed. Pile a generous handful of Gruyère (and Parmesan cheese if using) over the bread, covering it completely and letting it drape over the edges of the crock slightly.

9. 9

   Carefully place the baking sheet with the filled crocks under the broiler, about 6 inches from the heat. Broil for 3–5 minutes, watching closely, until the cheese is fully melted, bubbly, and has golden-brown spots. Remove carefully — the crocks will be extremely hot. Let rest for 2 minutes before serving.