In a large bowl, combine sausage, bread crumbs, milk and Italian seasoning. Form into 36 meatballs.
Heat a large nonstick skillet over medium heat and coat with nonstick cooking spray. Add onion and garlic; cook 3 minutes. Stir in diced tomatoes and tomato sauce; bring to a simmer.
Add meatballs to sauce. Cook, covered, on medium-low for 5 minutes. Turn meatballs and cook an additional 5 minutes. Meanwhile, cook cavatappi as per package directions, about 8 minutes. Drain, reserving 1 cup of the pasta cooking water.
Spoon meatballs and sauce plus reserved pasta water over pasta. Sprinkle with cheese, if desired. Serve with Radicchio and Shaved Fennel, if desired.
Combine 2 tbsp olive oil, 1 tbsp balsamic vinegar, 1/2 tsp mustard and a pinch of salt and pepper. Toss with 1 head sliced radicchio and 1 bulb thinly sliced fennel. Top with shaved Parmesan.