Onion Soup Gratin

• 3 tablespoons butter
• 4 onions, sliced thinly
• 2 tablespoons sugar
• 2 (14 1/2 ounce) cans beef broth
• 1 tablespoon balsamic vinegar or 1 tablespoon red wine vinegar
• salt and pepper
• 4 slices toasted French bread
• 1 cup grated swiss cheese

1. In large soup pot over medium heat, melt the butter.
2. Add the onions, cover and slowly cook until soft and translucent, stirring occasionally, about 15 minutes.
3. Add sugar and continue to cook until caramelized and rich brown in color, about 10 more minutes.
4. Add broth, vinegar, and salt and pepper to taste.
5. Simmer, covered for 20 minutes.
6. Heat broiler.
7. Ladle soup into 4 oven proof bowls.
8. Top each with a piece of toasted bread and 1/4 of the cheese.
9. Broil until cheese is melted and golden.
10. Be careful removing bowls from boiler.

butter, onions, sugar, beef broth, balsamic vinegar, salt, bread, swiss cheese

Taken from www.food.com/recipe/onion-soup-gratin-10293 (may not work)