Bistro French Onion Soup

Name: Bistro French Onion Soup
Prep time: 25 min
Cook time: 1 h 45 min
Total time: 2 h 10 min
Cuisine: European, Mediterranean, French
Ingredients: 1 stick unsalted butter; 5 cups sliced yellow onions (about 3 large onions); 1 cup sherry; 4 cups beef or vegetable stock; 1 bouquet garni (a few sprigs each of parsley, thyme, rosemary and sage tied together with twine); 1 bay leaf; Salt and freshly ground black pepper; 8 slices of baguette, toasted; 10 ounces shredded Gruyère cheese (or other similar Alpine cheese)