Classic French Onion Soup with Gruyère Croutons

Ingredients

Instructions

1. 1 Melt the butter in a large pot over medium heat.
2. 2 Add the sliced onions and cook, stirring occasionally, until they are soft and caramelized, about 25-30 minutes.
3. 3 Sprinkle the sugar, salt, and black pepper over the onions and stir well.
4. 4 Stir in the flour and cook for another 2 minutes, stirring constantly.
5. 5 Add the white wine to the pot, scraping up any browned bits from the bottom.
6. 6 Pour in the beef broth and add the thyme. Bring to a simmer and cook for 20 minutes.
7. 7 Stir in the balsamic vinegar and adjust seasoning with salt and pepper to taste.
8. 8 Preheat the broiler. Place the toasted baguette slices on a baking sheet and sprinkle each with grated Gruyère cheese.
9. 9 Broil until the cheese is melted and bubbly, about 2-3 minutes.
10. 10 Ladle the soup into bowls and top each with a Gruyère crouton before serving.