3 pounds white onions (3 or 4 large)
4 medium leeks
4 ounces pancetta, in 1 piece
1/4 cup extra-virgin olive oil
6 cups chicken stock
3 to 4 tablespoons balsamic vinegar
3/4 to 1 cup fruity red wine, such as Merlot or Beaujolais
Salt and pepper, to taste
6 slices rustic country style bread
2 garlic cloves, peeled, halved
3 ounces Parmesan cheese, in 1 chunk
2 tablespoons fresh parsley, chopped
Peel the onions and cut in half lengthwise. Thinly slice crosswise. Trim the leeks and cut in half lengthwise. Slice crosswise in 1/4-inch slices, using 3 inches of pale green. Place the leeks in cold water, and rinse to remove the dirt. Drain. Reserve the onions and leeks.
Unroll the pancetta and dice into 1/4-inch pieces. Heat the olive oil in a large soup pot over medium-high heat. Add the pancetta and cook until some of the fat has been rendered, about 5 minutes. Add the onions and leeks. Sauté for 20 minutes or until tender, stirring occasionally. Add the stock, and simmer 30 minutes. Stir the vinegar, wine, salt, and pepper into the soup. Cook until thoroughly heated.
Toast the bread slices, and rub with the peeled garlic clove halves.
Spoon the soup into soup bowls. Float the bread croutons in the soup. Pare 4 or 5 shavings of the cheese on top of each serving. Garnish with the chopped parsley, and serve immediately.