Panera Bistro French Onion Soup

4 sweet onions, sliced
1 tablespoon butter
1 tablespoon olive oil
1 teaspoon sugar
1 teaspoon thyme
1/2 teaspoon basil
4 cans sodium reduced beef broth
1/4 cup sherry
1 tablespoon balsamic reduction
cheese croutons
shredded gruyere and asiago, for garnish

In a large pot, saute sliced onions with the butter and olive oil.
Add the sugar as this will help caramelize.
Cook for 20-30 minutes until nicely browned. Add the thyme, basil, and season with salt and pepper, to taste. Cook for 1 minute.
Add the beef broth and let simmer for 30 minutes. Add the sherry and the vinegar. Simmer for additional 5 minutes.
Pour into individual bowls. Garnish with croutons and cheese. Serve immediately. If you would like melted cheese, broil the soup for a minute.