Preheat oven to 350°F.

(Optional) Saute broccoli, carrots, onion, garlic, and spinach in oil until tender.

Cook shells to package directions; drain (cool in a single layer on wax paper). Combine cheeses, parsley, salt and pepper, and optional veggies for filling; spoon in shells.

Spread a thin layer of sauce in a 9x13" baking dish and arrange shells in a single layer over sauce. Cover with remaining sauce. Cover with aluminum foil and bake for about 40 minutes.

Remove foil, add extra mozzarella cheese on top, and bake 15 minutes longer.