Roasted Garlic And Watercress Soup

Name: Roasted Garlic And Watercress Soup
Ingredients: 3 heads of garlic; 2 pieces of bacon, plus 2 more; 2 leeks, cleaned and cut in a medium dice; 1 large white onion, medium dice; 2 celery, medium dice; Bay leaf; 2 1/2 cups homemade chicken stock; 1 cup watercress, chopped; Olive oil; Kosher salt