Heat a 2-count of oil in a large soup pot over medium heat. Add the onion, garlic, and herbs and cook until softened, about 5 minutes. Add the tomato and cook until the vegetables cook down to a pulp, about 5 more minutes. Stir in the lamb and then the chicken broth. Bring to a simmer and season with salt and pepper. Simmer until the lamb is very tender, 20 to 30 minutes. Add the beans and simmer until warmed through. Then mash some of the beans against the side of the pot to break them down and thicken the soup. Season with salt and pepper and a drizzle of olive oil. Ladle the soup into bowls, top with fennel, and serve hot.