1. Preheat oven to broil. In a large soup pot, melt 4 tablespoons butter over medium-high heat and sauté one large thinly sliced onion until translucent.
2. Meanwhile, place 6 thick slices of French bread on a baking sheet and put under broiler. Toast one side, turn, place a slice of provolone cheese on top and toast until cheese is melted. Set aside.
3. When onions are translucent, add 4 cups water and the mix to pot, bring to a simmer over medium heat. Turn off heat.
4. Pour equal portions of soup into 6 bowls. Distribute any remaining onions evenly into bowls.
5. Place a slice of toasted cheese bread on top of each bowl of soup and serve immediately.