Add half of the chopped herbs, plus bay leaves, onion, carrot, celery, and green pepper, and stir until vegetables turn bright and begin to soften, about 3 minutes. Add tomato purée and stir, deglazing pan bottom and cooking until mixture begins to stick slightly, about 5 minutes. Add broth and bouillon cubes; bring to a boil, and then reduce heat to maintain a steady simmer. Cook uncovered for about 15 minutes, stirring from time to time to prevent sticking, until mixture reaches a gravy consistency. Stir in chopped chocolate, remaining herbs, and salt and pepper to taste.