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Ingredients
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Soup
Topping & Serving
Method
Soup
- 1
- 2
Melt butter and heat oil
In a large heavy-bottomed pot or Dutch oven, melt 3 tablespoons butter with 1 tablespoon olive oil over medium heat. The oil helps prevent the butter from browning too quickly.
- 3
Caramelize onions
Add the sliced onions, 1 teaspoon salt, 1 teaspoon freshly ground black pepper, and 1 teaspoon sugar to the pot. Cook over medium to medium-low heat, stirring every few minutes, for 30–40 minutes until onions are deep golden brown and sweet. If they stick or look dry, reduce heat slightly and add a splash of water or 1 teaspoon butter. Patience is key — proper caramelization develops the soup's flavor.
- 4
Add flour
Sprinkle 1 tablespoon all-purpose flour over the caramelized onions and stir for 1–2 minutes to cook the raw flour taste. This will slightly thicken the soup and help bind flavors.
- 5
Deglaze with wine
Pour in 1 cup dry white wine (optional) and scrape up any browned bits from the bottom of the pot with a wooden spoon. Simmer until wine is mostly evaporated, about 2–3 minutes.
- 6
Add stock and aromatics
Add 4 cups beef stock and 1 cup water to the pot. Stir in 1 bay leaf, 3 sprigs fresh thyme, and 1 teaspoon Worcestershire sauce. Bring the soup to a gentle simmer, then reduce heat to low and simmer uncovered for 20–25 minutes to meld flavors. Taste and adjust seasoning with additional salt and pepper if needed. Remove and discard the bay leaf and thyme stems; you can strip any remaining thyme leaves back into the soup for more fragrance.
Topping & Serving
- 7
Prepare bread
While the soup simmers, preheat your oven to 375°F (190°C). Lightly brush both sides of 6 baguette slices with 1 tablespoon melted butter. Place slices on a baking sheet and toast in the oven until golden and crisp, about 8–10 minutes, flipping once. Alternatively, broil briefly watching carefully to avoid burning.
- 8
Assemble bowls
Ladle the hot soup into ovenproof bowls or crocks, filling to about 3/4 full. Place 1 or 2 toasted bread slices on top of each bowl of soup (you can break slices to fit). Sprinkle about 1/3 to 1/2 cup grated Swiss cheese evenly over each bowl so the bread is well covered.
- 9
Broil to melt cheese
Set oven to broil with rack about 6 inches from the heating element. Place the filled bowls on a rimmed baking sheet and broil for 2–4 minutes until the cheese is bubbly and beginning to brown. Watch constantly to prevent burning. Alternatively, bake at 400°F (200°C) until cheese melts, about 6–8 minutes.
- 10