1. Prepare pasta according to directions. Drain and set aside. Preheat oven to 350°. Lightly grease a 13- x 9-inch baking dish.
2. Heat butter in a Dutch oven over medium-high heat; sauté onion 5 minutes or until just brown. Add garlic, and cook about 1 minute. Reduce heat to medium-low, and add greens; cover and cook 15 to 20 minutes or until greens are tender, stirring occasionally.
3. Sprinkle greens with flour. Cook uncovered, stirring constantly, 1 minute. Gradually add milk, stirring well. Cook 5 minutes, stirring often, until thickened and smooth. Remove from heat; stir in cooked pasta, mozzarella, and next 5 ingredients. Place into prepared dish, and sprinkle evenly with Parmesan.
4. Bake at 350° for 15 to 20 minutes.