In a large pot over medium heat, heat the olive oil. Stir in sausage, onion and fennel seeds and cook until sausage is brown, 10 minutes. Stir in carrots and celery and continue to cook and stir until vegetables begin to color, 5 minutes. Stir in tomatoes, parsley, basil and chicken stock. Bring to a boil, then reduce heat and simmer 20 minutes, until vegetables are tender.
Stir in pasta, salt and pepper, cook until pasta is tender, 10 minutes more. Serve topped with grated Parmesan.