- 1/3 cup butter
- 10 onions, peeled and thinly sliced
- 2 cloves garlic, crushed
- 1 (12 fluid ounce) can or bottle beer
- 1 quart beef broth
- 1/2 teaspoon dry mustard
- 1 teaspoon dried thyme
- 1/4 teaspoon ground black pepper
- 1 bay leaf
- 6 slices French bread, toasted
- 3 cups shredded Gruyere cheese
- In a large saucepan over medium heat, melt butter. Stir and cook onions in butter until golden brown, 15 minutes.
- Stir in the garlic and cook 1 minute. Pour in the beer and beef broth and season with mustard, thyme, black pepper and the bay leaf. Bring to a boil, then reduce heat, cover and simmer 30 minutes.
- Preheat oven to 425 degrees F (220 degrees C).
- Remove bay leaf from soup and ladle soup into a large casserole or individual ovenproof bowls, leaving about 1 inch of room at the top of the dish or dishes. Float slices of toasted bread on the soup and pile generously with Gruyere.
- Bake in preheated oven 10 minutes, until cheese is lightly browned and bubbly.