Ingredients
3 tablespoons unsalted butter, cut into 3 pieces
6 large onions (3 yellow onions and 3 red onions), sliced
1 teaspoon salt, plus more to taste
2 cups water, plus 3/4 cup for deglazing
1 tablespoon balsamic vinegar
1/4 cup dry red wine
4 cups low-sodium chicken broth
1 cup beef broth or beef stock
1 can (about 10 oz) organic beef consommé
Worcestershire sauce, a dash or two
6 sprigs fresh thyme
1 bay leaf
Ground black pepper to taste
For the cheese croutons:
1 baguette, cut into 1/2-inch slices
4 1/2 ounces Swiss cheese, sliced thin
1 1/2 ounces Gruyere cheese, grated (about 3/4 cup)
Instructions
1. Adjust oven rack to lower-middle position and heat oven to 400 degrees F. Generously spray inside of a heavy-bottomed large Dutch oven (at least 7-quart) with nonstick cooking spray.
2. Place butter in pot and add onions and 1 teaspoon salt. Cook covered for 1 hour. Onions will be moist and slightly reduced in volume.
3. Remove pot from oven and stir onions, scraping bottom and sides. Return pot to oven with lid slightly ajar and continue to cook until onions are very soft and golden brown, 1 1/2 to 1 3/4 hours longer, stirring and scraping after 1 hour.
4. Remove pot from oven and place over medium-high heat. Cook onions, stirring frequently and scraping bottom and sides of pot with a wooden spoon, until liquid evaporates and onions brown, 15 to 20 minutes. Reduce to medium heat if browning too quickly.
5. Continue to cook, stirring frequently, until pot bottom is coated with a dark crust, 6 to 8 minutes.
6. Add 1/4 cup water, scraping pot bottom to loosen crust. Cook until water evaporates and another dark crust forms, 6 to 8 minutes. Repeat deglazing process 2 to 3 more times until onions are very dark brown.
7. Add wine and balsamic vinegar, stirring frequently, until wine evaporates, about 5 minutes.
8. Stir in chicken broth, beef broth, consommé, 2 cups water, Worcestershire sauce, fresh thyme sprigs, and bay leaf (tied with twine). Add 1/2 teaspoon salt and scrape up any remaining crust from the bottom of the pot. Increase heat to high and bring to a simmer.
9. Reduce heat to low, cover, and simmer 30 minutes. Remove and discard herbs. Season with salt and black pepper to taste.
10. Arrange baguette slices on a rimmed baking sheet and bake at 400 degrees until dry, crisp, and golden at edges, about 10 minutes.
11. To serve: adjust oven rack 4 to 6 inches from broiler and heat broiler. Set oven-safe bowls on a rimmed baking sheet. Fill each with about 1 1/2 cups soup. Top with two toasted baguette slices. Layer Swiss cheese slices over the bread. Sprinkle about 2 tablespoons grated Gruyere over each bowl. Broil until well browned and bubbly, 7 to 10 minutes. Watch carefully.
Notes
The soup base can be made a day ahead and stored in an airtight container in the refrigerator — the flavor actually improves overnight. Make fresh croutons when you are ready to serve.
Store leftover soup and croutons separately. The soup keeps in an airtight container in the refrigerator for 3 to 4 days. Reheat on the stovetop over medium-low heat.
Dry white wine, dry vermouth, or dry sherry can be substituted for the red wine.
All Gruyere can be used in place of the Swiss and Gruyere combination.
- Prep Time: 20
- Cook Time: 30 hours 30 minutes
- Category: Soup
- Cuisine: French