Bring lentils and cinnamon stick to a boil in the broth. Simmer for 30 minutes. Remove cinnamon and discard. Saute onion, garlic, salt, turmeric, cumin seed, cumin and bay leaves in oil for 8 minutes. Add to the lentil mixture. Add tomatoes and simmer for 15 minutes. Remove and discard bay leaves. Add chickpeas and simmre for 5 minutes. Season with pepper, cayenne and lemon juice. Remove from heat. Serve sprinkled with mint.