The bistro starter of every Francophile’s dreams: slowly cooked sweet onions married to beef broth, ladled into crocks, topped with toasty baguette croûtes and a thick layer of Gruyère and Parmesan, and gratinéed under the broiler.
Special equipment: You’ll need 6 ovenproof crocks or ramekins with a capacity of 1 1/2 cups for this recipe.
- Yield: 6 servings
- Difficulty: Easy
- Total: About 2 hrs
- Active: 25 mins
- 4 tablespoons unsalted butter (1/2 stick)
- 2 pounds yellow onions, thinly sliced
- 3 fresh thyme sprigs
- 1 bay leaf
- 1 teaspoon kosher salt, plus more to taste
- 2 teaspoons all-purpose flour
- 3/4 cup dry white wine
- 4 cups beef broth
- 1 1/2 cups water
- Freshly ground black pepper, to taste
- 6 (1/2-inch) slices from a baguette loaf, cut on the diagonal
- 8 ounces Gruyère cheese, shredded
- 2 tablespoons finely grated Parmesan cheese
- Melt the butter in a large Dutch oven or heavy soup pot over medium-low heat. Add the onions, thyme, bay leaf, and measured salt. Slowly melt the onions, stirring frequently until the onions are very soft and a deep golden brown, about 45 minutes (if, at any point, the onions appear to be getting too dark, or beginning to stick to the pan, reduce the heat). Add the flour, stir well to combine it with the onions, and cook, stirring, for 1 minute. Add the wine and simmer, stirring, for 2 minutes. Add the broth and water, bring it to a boil, and simmer gently, stirring occasionally, for 30 minutes. Taste and season with additional salt, if necessary, and pepper.
- Heat the oven to 350°F and arrange a rack in the middle. Arrange the baguette slices in a single layer on a baking sheet and toast for 8 minutes. Turn the slices over and toast an additional 7 minutes.
- Turn on the broiler and arrange the crocks on a rimmed baking sheet or in a shallow baking pan.
- Pick the bay leaf and thyme sprigs out of the soup and discard them. Ladle the soup evenly among the crocks, then top each with a baguette toast. Sprinkle the crocks with the shredded Gruyère and grated Parmesan. Broil, about 4 to 5 inches from the heat, until the cheese is melted and bubbly, about 2 minutes. Serve immediately.