Ingredients
Soup and toast
- 2.5 lb yellow onions about 4–5 large; peeled, halved and thinly sliced (1.13 kg)
- 3 tbsp unsalted butter 42 g
- 2 cloves garlic minced
- 0.5 cup dry white wine 120 ml; use extra broth for a wine-free version
- 6 cups unsalted beef broth 1.42 L
- 1 tsp fresh thyme leaves
- 1 bay leaf
- 0.5 tsp kosher salt adjust to taste after simmering
- 3 tbsp water up to, only if needed to loosen browned bits
- 0.5 tsp black pepper
- 8 slices baguette ½ inch thick, about 120 g total
- 4 oz Gruyère cheese freshly grated (113 g)
Equipment
- Wide 5- to 6-quart heavy pot with lid
- Wooden spoon
- Chef’s knife and cutting board
- Rimmed baking sheet
- Grater
- Ladle
- Spatula
- Oven with broiler
Instructions
Cook the soup and toast
- Melt the butter in a wide 5- to 6-quart pot over medium heat. Add the sliced onions and kosher salt, cover, and cook for 8–10 minutes, stirring once, until wilted.
- Uncover and reduce the heat to medium-low. Cook for 45–60 minutes, stirring every few minutes and more often near the end, until the onions are evenly deep golden to copper brown. If the brown film begins to catch, add water a tablespoon at a time, using up to 3 tablespoons, and scrape it up; lower the heat if anything smells scorched.
- Stir in the garlic for 30 seconds. Pour in the wine and scrape the pot bottom. Simmer for 3–4 minutes, until most of the liquid has reduced.
- Add the broth, thyme, bay leaf, and pepper. Bring to a gentle simmer, then cook uncovered for 20 minutes. Remove the bay leaf and taste before adding any more salt.
- During the final minutes of simmering, heat the oven to 425°F (220°C). Arrange the baguette slices on a rimmed baking sheet and toast for 5–7 minutes, until the edges are crisp. Divide the cheese among the toasts. Switch to broil and broil for 1–2 minutes, watching constantly, until melted and lightly browned.
- Ladle the hot soup into four bowls. Use a spatula to place two cheese toasts on each bowl just before serving, or serve them alongside.
Video
Notes
Cooking times are a guide: the onions may need longer to become evenly deep golden. Keep the cheese toast separate until serving. For a wine-free version, use ½ cup extra broth and adjust brightness to taste. Cool soup promptly in shallow containers; refrigerate within 2 hours (1 hour above 90°F) and use within 3–4 days. Bring the soup to a rolling boil when reheating.
Technique video: John Kanell of Preppy Kitchen demonstrates stovetop onion caramelization and cheesy bread. His version includes flour and brandy and broils the filled bowls; this version omits both and melts the cheese on a baking sheet.