Costco French Onion Soup
A from-scratch French onion soup with deeply caramelized onions, a rich broth, and melted Gruyère over toasted baguette.
Ingredients
- 4 large yellow onions thinly sliced
- 2 tablespoons butter
- 2 tablespoons olive oil
- 1 1/2 teaspoons salt plus more to taste
- 2 cloves garlic minced
- 1 tablespoon fresh thyme or 1 teaspoon dried
- 2 teaspoons all-purpose flour
- 6 cups beef broth
- 1 bay leaf
- 1/2 teaspoon black pepper plus more to taste
- 1/4 teaspoon red wine vinegar or sherry vinegar
- 1 baguette sliced into 3/8-inch rounds
- Olive oil for brushing the bread
- 1 cup grated Gruyère cheese
Instructions
- Heat the butter and olive oil in a large pot. Add the onions and salt, cover for 3 to 4 minutes.
- Uncover and cook for 40 to 45 minutes, stirring every 8 to 10 minutes, until deeply golden.
- Brush baguette slices with olive oil and bake at 350°F for 10 minutes per side, until crisp.
- Stir in the garlic and thyme, then sprinkle the flour over the onions and toast for 1 minute.
- Add the beef broth, bay leaf, and pepper. Bring to a boil, then simmer uncovered for 10 minutes.
- Stir in the vinegar, adjust seasoning, and remove the bay leaf.
- Ladle soup into oven-safe bowls, top with toasted bread and Gruyère, and broil until golden and bubbling.
Notes
- Give the onions the full 40 plus minutes. Shortcutting this step is the biggest reason homemade versions taste flat compared to restaurant ones.
- Toast the bread separately so it holds up under the cheese instead of turning mushy in the broth.
- The small amount of flour toasted with the onions adds body to the broth without making it feel thickened.
- The vinegar at the end balances the sweetness from the caramelized onions, don't skip it even though it's a small amount.
- Watch the broiler closely once the cheese goes under it, Gruyère can go from perfectly golden to burnt within a minute.