6 large red or yellow onions (about 3 pounds), peeled and thinly sliced root to stem (see How to Slice an Onion), about 10 cups of sliced onions total
4 Tbsp Olive oil
2 Tbsp butter
1 teaspoon of sugar
Salt
2 cloves garlic, minced
8 cups of beef stock, chicken stock, or a combination of the two (traditionally the soup is made with beef stock)
1/2 cup of dry vermouth or dry white wine
2 bay leaves
4 teaspoons of fresh thyme (can also use a few sprigs of fresh thyme) OR 1 teaspoon dried thyme
1/2 teaspoon freshly ground black pepper
2 Tbsp brandy (optional)
8 inch-thick slices of French bread or baguette
1 1/2 cups of grated Swiss Gruyere and a sprinkling of Parmesan