Pick through the beans and give them a rinse. Put them in a bowl and cover them with water by two inches. Let them soak overnight.Drain the beans and place them in a pot. Add the chicken stock and 4 cups of water. Bring to a boil, then reduce to a simmer. While the beans are cooking, cook the bacon in a large skillet over medium heat until just barely crisp. Remove to a paper towel lined plate. Add 2/3 of the bacon to the beans and reserve the rest for garnish.Drain the bacon grease from the pan and add the onions, carrots, and celery. Season them with some salt and pepper and cook until just beginning to soften, about 3 to 4 minutes. Add the garlic and tomato paste and cook for another minute or two. Add the vegetables to the beans. Add the bay leaf and give it a good stir. Cover and cook on low (to medium-low) until the beans are tender, about 1 1/2 hours. Add a cup of broth if the liquid level gets too low. When ready to serve, taste and add more salt and pepper if needed. If desired, stir in the tomatoes. Serve with chopped reserved bacon and chopped parsley.